Resolve pending commit links

Task: MIL-004#1
Task: MIL-004#2
Task: MIL-004#3
Task: MIL-004#4

.env.example

@@ -1,7 +1,9 @@
 # Copy to .env and fill in. .env is ignored by git; never commit it.
 
-# Sheety: the endpoint of the "prices" sheet and the Bearer token of the project
-SHEETY_ENDPOINT=https://api.sheety.co/<your-id>/<your-project>/prices
+# Sheety: the endpoints of the "prices" sheet (destinations) and the "users" sheet
+# (the club's customers, filled by a Google Form), and the Bearer token of the project
+SHEETY_PRICES_ENDPOINT=https://api.sheety.co/<your-id>/<your-project>/prices
+SHEETY_USERS_ENDPOINT=https://api.sheety.co/<your-id>/<your-project>/users
 SHEETY_TOKEN=
 
 # Flight provider: "serpapi" or "mock" (the course's mock flight service)
@@ -15,3 +17,9 @@ MOCK_FLIGHTS_APP_KEY=
 # WhatsApp: your own number with country code, for example +441234567890
 # Needs the optional extra: python -m pip install -e ".[whatsapp]"
 WHATSAPP_NUMBER=
+
+# Email: the SMTP server, the sender and an app password (not your normal password).
+# Every customer in the "users" sheet gets the deal by email.
+SMTP_ADDRESS=smtp.gmail.com
+EMAIL_ADDRESS=
+EMAIL_PASSWORD=

docs/artifact-registry.md

@@ -16,7 +16,7 @@ document of a type. `Primary File` may contain a glob (e.g.
 | PP | Project Plan | docs/project-plan.md | 002 |
 | MIL | Milestone | docs/milestones/mil-*.md | 006 |
 | ADR | Architecture Decision Record | docs/adr/adr-*.md | 0002 |
-| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 010 |
+| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 012 |
 
 ## Languages
 

docs/sqa/reviews/rc-010-code-mil-003.md

@@ -0,0 +1,61 @@
+# SQA Review Record
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-010 |
+| CrossReference | [MIL-003], [QC-PY-001], [ADR-0001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-24 | Accepted | Jens Tirsvad Nielsen | AI as stand-in for S01 | Initial version | [49061c1] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [MIL-003] (the Python code and tests of its tasks 1 to 4: `src/flight_club/`, `tests/`)
+- Checklist used: [QC-PY-001]
+- Scope: full review of the code changed by this milestone
+- Mode: autonomous, not independent (the reviewer is `AI as stand-in for S01`)
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | Packages, modules, functions, variables, classes and constants follow PEP 8 casing (`snake_case`, `PascalCase`, `UPPER_SNAKE`) | Pass | Names use snake_case, PascalCase and UPPER_SNAKE (`ENV_SHEETY_USERS_ENDPOINT`, `extract_emails`). |
+| 2 | Names state purpose in the domain's language; no unexplained abbreviations, no single-letter names outside tiny scopes | Pass | Names state purpose (`get_customer_emails`, `extract_emails`, `EMAIL_PATTERN`). |
+| 3 | Code is produced by the project's formatter and passes its linter with no unexplained suppressions | Pass | `ruff check` and `ruff format --check` pass; no new suppressions. |
+| 4 | Every function and method signature is type-annotated, including `-> None` | Pass | Every new function and test has annotations including `-> None`. |
+| 5 | No bare `except:`, no swallowed exceptions; specific exceptions are raised and the cause is kept (`raise ... from`) | Pass | No bare except; HTTP and shape problems raise `DataManagerError` with specific messages. |
+| 6 | No mutable default arguments and no shadowed builtins | Pass | No mutable defaults and no shadowed builtins; `_read_rows` is shared by both sheets. |
+| 7 | Files, locks and connections are managed with context managers | Pass | No files or connections opened by the new code; the HTTP session is unchanged. |
+| 8 | Public modules, classes and functions have docstrings that say what, not how | Pass | Public classes and functions carry Doxygen comments (what, not how). |
+| 9 | Logging uses `logging`, not `print`; no secrets or personal data in log output | Pass | Console output uses `print` as the assignment requires; recorded in [ADR-0001]. No secrets are printed. |
+| 10 | Classes and operations trace to the Design Class Diagram they implement; deviations are recorded | Pass | No DCD exists; the assignment's classes are the design; deviation recorded in [ADR-0001]. |
+| 11 | Tests exist for new behaviour, are named for the behaviour, and do not depend on order or the network | Pass | New behaviour is tested: users read, errors, missing users endpoint, email extraction, legacy endpoint name. Fakes only; no network or `.env`. |
+| 12 | Type checker runs in strict mode without errors; `Any` is justified in a comment | Pass | `mypy --strict` passes on `src` and `tests`; the only `Any` is the JSON response shape. |
+| 13 | Dependencies are declared and pinned in the project's dependency file, none unused | Pass | No new dependencies. |
+| 14 | Each piece of knowledge (a business rule, constant, format, validation or query) is defined in one place; code is merged only where it expresses the same knowledge, not where it merely looks alike | Pass | One private `_read_rows` serves both sheets; endpoint names, keys and the email pattern are constants. |
+| 15 | Imports point inward: business-rule modules import no framework, database, UI or delivery-mechanism code, and there are no import cycles | Pass | `flight_data` imports only `constants`; `main` wires the others; no import cycles. |
+| 16 | SOLID holds: a class or module has one reason to change; new behaviour is added by extension, not by editing a type test in several places; subclasses honour the contract of their base; protocols are narrow; high-level code depends on protocols or abstract types and receives its implementations | Pass | `get_destination_data` and `update_lowest_price` keep their contracts; the users endpoint is checked only when used, so Day 39 `.env` files still run. |
+| 17 | Source is laid out in the layers and folders of the clean architecture folder structure (`domain`, `application`, `infrastructure`, `presentation` packages under `src/`, and `unit`, `integration` and `e2e` under `tests/`), in `snake_case`, and imports between the layers point inward | Pass | Flat layout accepted by [ADR-0001] (merged layers). |
+| 18 | File and folder names are English, contain no space and no character outside letters, digits, `-`, `_` and `.`, and follow the casing of the language for files | Pass | File names are lower-case snake_case English with no spaces. |
+
+## Overall Verdict
+
+Go — all mandatory criteria pass; deviations are recorded in ADR-0001.
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | - | - |
+
+---
+
+[MIL-003]: ../../milestones/mil-003-customer-emails.md
+[QC-PY-001]: ../../../framework/qc/code/qc-programming-python.md
+[ADR-0001]: ../../adr/adr-0001-flat-module-layout-and-console-output.md
+[49061c1]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/49061c1105f9874e073f83048fd0020217a1600a

docs/sqa/reviews/rc-011-code-mil-004.md

@@ -0,0 +1,61 @@
+# SQA Review Record
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-011 |
+| CrossReference | [MIL-004], [QC-PY-001], [ADR-0001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-10-24 | Accepted | Jens Tirsvad Nielsen | AI as stand-in for S01 | Initial version | [d94a68a] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [MIL-004] (the Python code and tests of its tasks 1 to 4: `src/flight_club/`, `tests/`)
+- Checklist used: [QC-PY-001]
+- Scope: full review of the code changed by this milestone
+- Mode: autonomous, not independent (the reviewer is `AI as stand-in for S01`)
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | Packages, modules, functions, variables, classes and constants follow PEP 8 casing (`snake_case`, `PascalCase`, `UPPER_SNAKE`) | Pass | Names use snake_case, PascalCase and UPPER_SNAKE (`send_emails`, `ENV_SMTP_ADDRESS`, `SMTP_PORT`). |
+| 2 | Names state purpose in the domain's language; no unexplained abbreviations, no single-letter names outside tiny scopes | Pass | Names state purpose (`send_emails`, `_build_email`, `EMAIL_SUBJECT`). |
+| 3 | Code is produced by the project's formatter and passes its linter with no unexplained suppressions | Pass | `ruff check` and `ruff format --check` pass; no new suppressions. |
+| 4 | Every function and method signature is type-annotated, including `-> None` | Pass | Every new function and test has annotations including `-> None`. |
+| 5 | No bare `except:`, no swallowed exceptions; specific exceptions are raised and the cause is kept (`raise ... from`) | Pass | Only `smtplib.SMTPException` and `OSError` are caught, in one place; the error type is reported and the loop result is returned, nothing is swallowed silently. |
+| 6 | No mutable default arguments and no shadowed builtins | Pass | No mutable defaults (`is_direct: bool = True`, `stops: int = 0`); no shadowed builtins. |
+| 7 | Files, locks and connections are managed with context managers | Pass | The SMTP connection is opened with a `with` block, so it is always closed. |
+| 8 | Public modules, classes and functions have docstrings that say what, not how | Pass | Public classes and functions carry Doxygen comments (what, not how). |
+| 9 | Logging uses `logging`, not `print`; no secrets or personal data in log output | Pass | Output uses `print` as the program's console output, recorded in [ADR-0001]. The SMTP error text and the app password are never printed (test `never_raises_or_prints_the_login`). |
+| 10 | Classes and operations trace to the Design Class Diagram they implement; deviations are recorded | Pass | No DCD exists; the assignment's classes are the design; deviation recorded in [ADR-0001]. |
+| 11 | Tests exist for new behaviour, are named for the behaviour, and do not depend on order or the network | Pass | New behaviour is tested with a fake `smtplib.SMTP`: login and STARTTLS, one mail per address, UTF-8 body, missing settings, SMTP failure, both message texts, GBP and no pound sign, customers read once, WhatsApp still sent when customers cannot be read. No mail is sent; no `.env`. |
+| 12 | Type checker runs in strict mode without errors; `Any` is justified in a comment | Pass | `mypy --strict` passes on `src` and `tests`; the only `Any` is the JSON response shape. |
+| 13 | Dependencies are declared and pinned in the project's dependency file, none unused | Pass | No new dependencies. |
+| 14 | Each piece of knowledge (a business rule, constant, format, validation or query) is defined in one place; code is merged only where it expresses the same knowledge, not where it merely looks alike | Pass | The message text is built in one place (`build_message`) and reused for WhatsApp and email; env names, port and subject are constants. |
+| 15 | Imports point inward: business-rule modules import no framework, database, UI or delivery-mechanism code, and there are no import cycles | Pass | `flight_data` imports only `constants`; `main` wires the others; no import cycles. |
+| 16 | SOLID holds: a class or module has one reason to change; new behaviour is added by extension, not by editing a type test in several places; subclasses honour the contract of their base; protocols are narrow; high-level code depends on protocols or abstract types and receives its implementations | Pass | `send_emails` is added next to `send_whatsapp` without changing it; the SMTP class is the standard one and is replaced in tests by monkeypatching. |
+| 17 | Source is laid out in the layers and folders of the clean architecture folder structure (`domain`, `application`, `infrastructure`, `presentation` packages under `src/`, and `unit`, `integration` and `e2e` under `tests/`), in `snake_case`, and imports between the layers point inward | Pass | Flat layout accepted by [ADR-0001] (merged layers). |
+| 18 | File and folder names are English, contain no space and no character outside letters, digits, `-`, `_` and `.`, and follow the casing of the language for files | Pass | File names are lower-case snake_case English with no spaces. |
+
+## Overall Verdict
+
+Go — all mandatory criteria pass; deviations are recorded in ADR-0001.
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | - | - |
+
+---
+
+[MIL-004]: ../../milestones/mil-004-email-notifications-and-main.md
+[QC-PY-001]: ../../../framework/qc/code/qc-programming-python.md
+[ADR-0001]: ../../adr/adr-0001-flat-module-layout-and-console-output.md
+[d94a68a]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/040-personal-flight-club/commit/d94a68ac10edbcbd44b59f8f1f30c5aa14a9edb8

src/flight_club/constants.py

@@ -48,7 +48,13 @@ PROVIDER_SERPAPI = "serpapi"
 ## @brief Name of the mock flight provider.
 PROVIDER_MOCK = "mock"
 
-## @brief Environment variable: Sheety sheet endpoint.
+## @brief Environment variable: Sheety endpoint of the "prices" sheet.
+ENV_SHEETY_PRICES_ENDPOINT = "SHEETY_PRICES_ENDPOINT"
+
+## @brief Environment variable: Sheety endpoint of the "users" sheet (the club's customers).
+ENV_SHEETY_USERS_ENDPOINT = "SHEETY_USERS_ENDPOINT"
+
+## @brief Environment variable: the Day 39 name of the prices endpoint, still accepted.
 ENV_SHEETY_ENDPOINT = "SHEETY_ENDPOINT"
 
 ## @brief Environment variable: Sheety Bearer token.
@@ -72,12 +78,39 @@ ENV_MOCK_FLIGHTS_URL = "MOCK_FLIGHTS_URL"
 ## @brief Environment variable: WhatsApp recipient number with country code.
 ENV_WHATSAPP_NUMBER = "WHATSAPP_NUMBER"
 
+## @brief Environment variable: address of the SMTP server that sends the emails.
+ENV_SMTP_ADDRESS = "SMTP_ADDRESS"
+
+## @brief Environment variable: the sender's email address, also the SMTP login name.
+ENV_EMAIL_ADDRESS = "EMAIL_ADDRESS"
+
+## @brief Environment variable: the app password of the sender's email account.
+ENV_EMAIL_PASSWORD = "EMAIL_PASSWORD"
+
+## @brief Port of the SMTP server; the connection is upgraded with STARTTLS.
+SMTP_PORT = 587
+
+## @brief Subject line of the deal emails.
+EMAIL_SUBJECT = "New Low Price Flight!"
+
 ## @brief Seconds pywhatkit waits for WhatsApp Web to load before it sends the message.
 WHATSAPP_WAIT_SECONDS = 15
 
 ## @brief Seconds pywhatkit waits after sending before it closes the browser tab.
 WHATSAPP_CLOSE_SECONDS = 3
 
+## @brief Key that holds the rows in the Sheety response for the "prices" sheet.
+PRICES_KEY = "prices"
+
+## @brief Key that holds the rows in the Sheety response for the "users" sheet.
+USERS_KEY = "users"
+
+## @brief Field of a "users" row that holds the customer's email address.
+EMAIL_FIELD = "email"
+
+## @brief Pattern of an accepted email address: text, an at sign and a dotted domain.
+EMAIL_PATTERN = r"[^@\s]+@[^@\s]+\.[^@\s]+"
+
 ## @brief Seconds to wait for an HTTP response before giving up.
 REQUEST_TIMEOUT_SECONDS = 30
 

src/flight_club/data_manager.py

@@ -4,14 +4,21 @@
 """
 
 import os
+import re
 from typing import Any
 
 import requests
 
 from flight_club.constants import (
+    EMAIL_FIELD,
+    EMAIL_PATTERN,
     ENV_SHEETY_ENDPOINT,
+    ENV_SHEETY_PRICES_ENDPOINT,
     ENV_SHEETY_TOKEN,
+    ENV_SHEETY_USERS_ENDPOINT,
+    PRICES_KEY,
     REQUEST_TIMEOUT_SECONDS,
+    USERS_KEY,
 )
 
 
@@ -20,15 +27,27 @@ class DataManagerError(RuntimeError):
     pass
 
 
-## @brief Talks to the Sheety sheet that holds the destinations.
+## @brief Talks to the Sheety sheets: the destinations ("prices") and the customers ("users").
 class DataManager:
-    ## @brief Reads the endpoint and token from the environment.
+    ## @brief Reads every setting from the environment, in this one place.
+    #
+    #  The prices endpoint comes from SHEETY_PRICES_ENDPOINT, or from the Day 39 name
+    #  SHEETY_ENDPOINT. The users endpoint is optional here and checked when it is used,
+    #  so a run without customers still works.
     #  @param session Optional HTTP session; a new one is made per call if omitted.
     def __init__(self, session: requests.Session | None = None) -> None:
-        self._endpoint = self._require_env(ENV_SHEETY_ENDPOINT)
+        self._prices_endpoint = self._prices_endpoint_from_env()
+        self._users_endpoint = os.environ.get(ENV_SHEETY_USERS_ENDPOINT) or None
         self._headers = {"Authorization": f"Bearer {self._require_env(ENV_SHEETY_TOKEN)}"}
         self._session = session
 
+    @classmethod
+    def _prices_endpoint_from_env(cls) -> str:
+        legacy = os.environ.get(ENV_SHEETY_ENDPOINT)
+        if legacy and not os.environ.get(ENV_SHEETY_PRICES_ENDPOINT):
+            return legacy
+        return cls._require_env(ENV_SHEETY_PRICES_ENDPOINT)
+
     @staticmethod
     def _require_env(name: str) -> str:
         value = os.environ.get(name)
@@ -45,18 +64,43 @@ class DataManager:
         if not 200 <= response.status_code < 300:
             raise DataManagerError(f"Sheety {action} failed with HTTP {response.status_code}.")
 
-    ## @brief Fetch every destination row from the Google Sheet through the Sheety API.
-    #  @return Rows such as {'city': 'Paris', 'iataCode': 'CDG', 'lowestPrice': 54, 'id': 2}.
-    def get_destination_data(self) -> list[dict[str, Any]]:
+    def _read_rows(self, endpoint: str, key: str) -> list[dict[str, Any]]:
         response = self._get_session().get(
-            self._endpoint, headers=self._headers, timeout=REQUEST_TIMEOUT_SECONDS
+            endpoint, headers=self._headers, timeout=REQUEST_TIMEOUT_SECONDS
         )
         self._check(response, "read")
         body = response.json()
-        prices = body.get("prices") if isinstance(body, dict) else None
-        if not isinstance(prices, list):
-            raise DataManagerError("Sheety response has no 'prices' list.")
-        return prices
+        rows = body.get(key) if isinstance(body, dict) else None
+        if not isinstance(rows, list):
+            raise DataManagerError(f"Sheety response has no '{key}' list.")
+        return rows
+
+    ## @brief Fetch every destination row from the Google Sheet through the Sheety API.
+    #  @return Rows such as {'city': 'Paris', 'iataCode': 'CDG', 'lowestPrice': 54, 'id': 2}.
+    def get_destination_data(self) -> list[dict[str, Any]]:
+        return self._read_rows(self._prices_endpoint, PRICES_KEY)
+
+    ## @brief Fetch every customer row from the "users" sheet.
+    #  @return Rows such as {'firstName': 'Ann', 'email': 'ann@example.com', 'id': 2}.
+    def get_customer_emails(self) -> list[dict[str, Any]]:
+        if self._users_endpoint is None:
+            raise DataManagerError(f"Environment variable {ENV_SHEETY_USERS_ENDPOINT} is not set.")
+        return self._read_rows(self._users_endpoint, USERS_KEY)
+
+    ## @brief Picks the usable email addresses out of the customer rows.
+    #  @param customers Rows from get_customer_emails().
+    #  @return The addresses that look like an email address, in sheet order, without duplicates.
+    @staticmethod
+    def extract_emails(customers: list[dict[str, Any]]) -> list[str]:
+        emails: list[str] = []
+        for customer in customers:
+            email = customer.get(EMAIL_FIELD)
+            if not isinstance(email, str):
+                continue
+            email = email.strip()
+            if re.fullmatch(EMAIL_PATTERN, email) and email not in emails:
+                emails.append(email)
+        return emails
 
     ## @brief Stores a new lowest price for one row.
     #  @param row_id Sheety row id.
@@ -64,7 +108,7 @@ class DataManager:
     #  @return None
     def update_lowest_price(self, row_id: int, new_price: float) -> None:
         response = self._get_session().put(
-            f"{self._endpoint}/{row_id}",
+            f"{self._prices_endpoint}/{row_id}",
             json={"price": {"lowestPrice": new_price}},
             headers=self._headers,
             timeout=REQUEST_TIMEOUT_SECONDS,

src/flight_club/main.py

@@ -32,6 +32,14 @@ def _is_checkable(row: dict[str, object]) -> bool:
     )
 
 
+def _get_customer_emails(data_manager: DataManager) -> list[str]:
+    try:
+        return data_manager.extract_emails(data_manager.get_customer_emails())
+    except DataManagerError as error:
+        print(f"No emails sent: {error}")
+        return []
+
+
 ## @brief Checks every sheet row and reports each flight cheaper than the stored price.
 #  @param data_manager Source of the destination rows and target of price updates.
 #  @param flight_search Provider of flight offers.
@@ -49,6 +57,7 @@ def run(
     six_month_from_today = today + timedelta(days=SEARCH_WINDOW_DAYS)
     return_date = six_month_from_today.strftime(DATE_FORMAT)
     found: list[FlightData] = []
+    customer_emails: list[str] | None = None
 
     sheet_data = data_manager.get_destination_data()
     for row in sheet_data:
@@ -70,7 +79,11 @@ def run(
         if cheapest.price != NOT_AVAILABLE and cheapest.price < row["lowestPrice"]:
             print(f"Lower price flight found to {row['city']}!")
             data_manager.update_lowest_price(row["id"], cheapest.price)  # type: ignore[arg-type]
-            notification_manager.send_whatsapp(notification_manager.build_message(cheapest))
+            message = notification_manager.build_message(cheapest)
+            notification_manager.send_whatsapp(message)
+            if customer_emails is None:
+                customer_emails = _get_customer_emails(data_manager)
+            notification_manager.send_emails(customer_emails, message)
             found.append(cheapest)
     return found
 

src/flight_club/notification_manager.py

@@ -1,14 +1,21 @@
 """
 @file
-@brief Builds low price alerts and sends them through WhatsApp.
+@brief Builds low price alerts and sends them through email and WhatsApp.
 """
 
 import os
+import smtplib
 from collections.abc import Callable
+from email.message import EmailMessage
 
 from flight_club.constants import (
     CURRENCY,
+    EMAIL_SUBJECT,
+    ENV_EMAIL_ADDRESS,
+    ENV_EMAIL_PASSWORD,
+    ENV_SMTP_ADDRESS,
     ENV_WHATSAPP_NUMBER,
+    SMTP_PORT,
     WHATSAPP_CLOSE_SECONDS,
     WHATSAPP_WAIT_SECONDS,
 )
@@ -16,30 +23,78 @@ from flight_club.flight_data import FlightData
 
 _INSTALL_HINT = 'Install the optional extra with: pip install -e ".[whatsapp]"'
 _NUMBER_HINT = f"Set {ENV_WHATSAPP_NUMBER} (with country code) to receive WhatsApp messages."
+_EMAIL_HINT = (
+    f"Set {ENV_SMTP_ADDRESS}, {ENV_EMAIL_ADDRESS} and {ENV_EMAIL_PASSWORD} to send emails."
+)
 
 
-## @brief Formats flight alerts and delivers them to the owner's WhatsApp.
+## @brief Formats flight alerts and delivers them by email to the customers and to the owner's WhatsApp.
 class NotificationManager:
-    ## @brief Creates the manager with an optional replacement for pywhatkit.
+    ## @brief Reads every setting from the environment, in this one place.
     #  @param sender Callable taking (number, message); used instead of pywhatkit when given.
     def __init__(self, sender: Callable[[str, str], None] | None = None) -> None:
         self._sender = sender
+        self._smtp_address = os.environ.get(ENV_SMTP_ADDRESS)
+        self._email_address = os.environ.get(ENV_EMAIL_ADDRESS)
+        self._email_password = os.environ.get(ENV_EMAIL_PASSWORD)
+        self._whatsapp_number = os.environ.get(ENV_WHATSAPP_NUMBER)
 
     ## @brief Builds the alert text for one cheap flight.
+    #
+    #  A direct flight gets the short text; a flight with stopovers says how many.
+    #  The price uses the currency code (GBP), never a currency symbol.
     #  @param flight The cheapest flight found for a destination.
     #  @return A one line message with price, airports and both dates.
     def build_message(self, flight: FlightData) -> str:
-        return (
+        message = (
             f"Low price alert! Only {CURRENCY} {flight.price} to fly "
             f"from {flight.origin_airport} to {flight.destination_airport}, "
             f"from {flight.out_date} to {flight.return_date}."
         )
+        if flight.stops == 0:
+            return message
+        noun = "stopover" if flight.stops == 1 else "stopovers"
+        return f"{message} Flight has {flight.stops} {noun}."
+
+    ## @brief Sends the message to every address; never raises.
+    #
+    #  The mail is encoded as UTF-8, so non-ASCII characters do not fail.
+    #  @param email_list Recipient addresses.
+    #  @param email_body The text of the mail.
+    #  @return The number of mails that were sent; 0 when the SMTP settings are missing.
+    def send_emails(self, email_list: list[str], email_body: str) -> int:
+        if not email_list:
+            return 0
+        if not (self._smtp_address and self._email_address and self._email_password):
+            print(_EMAIL_HINT)
+            print(email_body)
+            return 0
+        sent = 0
+        try:
+            with smtplib.SMTP(self._smtp_address, SMTP_PORT) as connection:
+                connection.starttls()
+                connection.login(self._email_address, self._email_password)
+                for address in email_list:
+                    connection.send_message(self._build_email(address, email_body))
+                    sent += 1
+        except (smtplib.SMTPException, OSError) as error:
+            # Only the type is printed: the text of the error might echo the login.
+            print(f"Sending email failed: {type(error).__name__}.")
+        return sent
+
+    def _build_email(self, address: str, email_body: str) -> EmailMessage:
+        message = EmailMessage()
+        message["Subject"] = EMAIL_SUBJECT
+        message["From"] = self._email_address
+        message["To"] = address
+        message.set_content(email_body, charset="utf-8")
+        return message
 
     ## @brief Sends a message to the number in the environment; never raises.
     #  @param message The text to send.
     #  @return True when sent, False when it was only printed.
     def send_whatsapp(self, message: str) -> bool:
-        number = os.environ.get(ENV_WHATSAPP_NUMBER)
+        number = self._whatsapp_number
         if not number:
             return self._print_instead(_NUMBER_HINT, message)
         if self._sender is not None:

tests/test_data_manager.py

@@ -7,12 +7,15 @@ from flight_club.constants import REQUEST_TIMEOUT_SECONDS
 from flight_club.data_manager import DataManager, DataManagerError
 
 ENDPOINT = "https://api.sheety.co/abc/flights/prices"
+USERS_ENDPOINT = "https://api.sheety.co/abc/flights/users"
 TOKEN = "super-secret-token"
 
 
 @pytest.fixture(autouse=True)
 def _env(monkeypatch: pytest.MonkeyPatch) -> None:
-    monkeypatch.setenv("SHEETY_ENDPOINT", ENDPOINT)
+    monkeypatch.delenv("SHEETY_ENDPOINT", raising=False)
+    monkeypatch.setenv("SHEETY_PRICES_ENDPOINT", ENDPOINT)
+    monkeypatch.setenv("SHEETY_USERS_ENDPOINT", USERS_ENDPOINT)
     monkeypatch.setenv("SHEETY_TOKEN", TOKEN)
 
 
@@ -75,10 +78,70 @@ def test_errors_never_contain_token() -> None:
     assert TOKEN not in str(write_error.value)
 
 
-@pytest.mark.parametrize("name", ["SHEETY_ENDPOINT", "SHEETY_TOKEN"])
+@pytest.mark.parametrize("name", ["SHEETY_PRICES_ENDPOINT", "SHEETY_TOKEN"])
 def test_missing_env_variable_names_the_variable(
     monkeypatch: pytest.MonkeyPatch, name: str
 ) -> None:
     monkeypatch.delenv(name)
     with pytest.raises(DataManagerError, match=name):
         DataManager(_session())
+
+
+USERS = [
+    {"firstName": "Ann", "lastName": "Lee", "email": "ann@example.com", "id": 2},
+    {"firstName": "Bo", "lastName": "Kim", "email": " bo@example.com ", "id": 3},
+]
+
+
+def test_get_customer_emails_returns_users() -> None:
+    session = _session(body={"users": USERS})
+    assert DataManager(session).get_customer_emails() == USERS
+    session.get.assert_called_once_with(
+        USERS_ENDPOINT,
+        headers={"Authorization": f"Bearer {TOKEN}"},
+        timeout=REQUEST_TIMEOUT_SECONDS,
+    )
+
+
+@pytest.mark.parametrize("body", [{}, {"users": "x"}, [1]])
+def test_get_customer_emails_raises_without_users_list(body: Any) -> None:
+    with pytest.raises(DataManagerError, match="users"):
+        DataManager(_session(body=body)).get_customer_emails()
+
+
+def test_get_customer_emails_raises_on_http_error() -> None:
+    with pytest.raises(DataManagerError, match="401"):
+        DataManager(_session(status=401)).get_customer_emails()
+
+
+def test_get_customer_emails_needs_the_users_endpoint(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.delenv("SHEETY_USERS_ENDPOINT")
+    manager = DataManager(_session(body={"users": USERS}))
+    with pytest.raises(DataManagerError, match="SHEETY_USERS_ENDPOINT"):
+        manager.get_customer_emails()
+
+
+def test_extract_emails_keeps_valid_unique_addresses() -> None:
+    customers: list[dict[str, Any]] = [
+        *USERS,
+        {"email": "ann@example.com"},
+        {"email": "not-an-email"},
+        {"email": None},
+        {"firstName": "No", "lastName": "Mail"},
+    ]
+    assert DataManager.extract_emails(customers) == ["ann@example.com", "bo@example.com"]
+
+
+def test_legacy_endpoint_name_is_still_accepted(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.delenv("SHEETY_PRICES_ENDPOINT")
+    monkeypatch.setenv("SHEETY_ENDPOINT", "https://api.sheety.co/old/prices")
+    session = _session(body={"prices": []})
+    DataManager(session).get_destination_data()
+    assert session.get.call_args.args == ("https://api.sheety.co/old/prices",)
+
+
+def test_prices_endpoint_wins_over_the_legacy_name(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setenv("SHEETY_ENDPOINT", "https://api.sheety.co/old/prices")
+    session = _session(body={"prices": []})
+    DataManager(session).get_destination_data()
+    assert session.get.call_args.args == (ENDPOINT,)

tests/test_main.py

@@ -15,6 +15,8 @@ class FakeDataManager:
     def __init__(self, rows: list[dict[str, Any]]) -> None:
         self.rows = rows
         self.updates: list[tuple[int, float]] = []
+        self.customers_error: Exception | None = None
+        self.customer_reads = 0
 
     def get_destination_data(self) -> list[dict[str, Any]]:
         return self.rows
@@ -22,6 +24,16 @@ class FakeDataManager:
     def update_lowest_price(self, row_id: int, new_price: float) -> None:
         self.updates.append((row_id, new_price))
 
+    def get_customer_emails(self) -> list[dict[str, Any]]:
+        if self.customers_error is not None:
+            raise self.customers_error
+        self.customer_reads += 1
+        return [{"email": "ann@example.test"}, {"email": "bo@example.test"}]
+
+    @staticmethod
+    def extract_emails(customers: list[dict[str, Any]]) -> list[str]:
+        return [str(c["email"]) for c in customers]
+
 
 class FakeFlightSearch:
     def __init__(self, price: float | None, indirect_price: float | None = None) -> None:
@@ -54,6 +66,11 @@ class FakeFlightSearch:
 class FakeNotificationManager:
     def __init__(self) -> None:
         self.sent: list[str] = []
+        self.emails: list[tuple[list[str], str]] = []
+
+    def send_emails(self, email_list: list[str], email_body: str) -> int:
+        self.emails.append((email_list, email_body))
+        return len(email_list)
 
     def build_message(self, flight: FlightData) -> str:
         return f"alert {flight.destination_airport} {flight.price}"
@@ -165,3 +182,39 @@ def test_run_reports_nothing_when_neither_search_finds_a_flight() -> None:
     assert search.direct_flags == [True, False]
     assert found == []
     assert data.updates == []
+
+
+def test_run_emails_every_customer_when_a_cheaper_flight_is_found() -> None:
+    _, _, _, notifier = _run([_row(100)], 54)
+    assert notifier.emails == [(["ann@example.test", "bo@example.test"], "alert CDG 54.0")]
+
+
+def test_run_sends_no_email_when_nothing_is_cheaper() -> None:
+    _, _, _, notifier = _run([_row(100)], 150)
+    assert notifier.emails == []
+
+
+def test_run_reads_the_customers_once_for_several_deals() -> None:
+    rows = [{**_row(), "iataCode": code, "id": i} for i, code in enumerate(["CDG", "BER"])]
+    data, search, notifier = FakeDataManager(rows), FakeFlightSearch(54), FakeNotificationManager()
+    run(data, search, notifier, today=TODAY)  # type: ignore[arg-type]
+    assert data.customer_reads == 1
+    assert len(notifier.emails) == 2
+
+
+def test_run_still_sends_whatsapp_when_the_customers_cannot_be_read(
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    data, search, notifier = (
+        FakeDataManager([_row(100)]),
+        FakeFlightSearch(54),
+        FakeNotificationManager(),
+    )
+    data.customers_error = DataManagerError(
+        "Environment variable SHEETY_USERS_ENDPOINT is not set."
+    )
+    found = run(data, search, notifier, today=TODAY)  # type: ignore[arg-type]
+    assert [f.price for f in found] == [54]
+    assert notifier.sent == ["alert CDG 54.0"]
+    assert notifier.emails == [([], "alert CDG 54.0")]
+    assert "SHEETY_USERS_ENDPOINT" in capsys.readouterr().out

tests/test_notification_manager.py

@@ -1,11 +1,18 @@
 import builtins
+import smtplib
 import sys
 import types
-from typing import Any
+from typing import Any, ClassVar, Self
 
 import pytest
 
-from flight_club.constants import ENV_WHATSAPP_NUMBER
+from flight_club.constants import (
+    ENV_EMAIL_ADDRESS,
+    ENV_EMAIL_PASSWORD,
+    ENV_SMTP_ADDRESS,
+    ENV_WHATSAPP_NUMBER,
+    SMTP_PORT,
+)
 from flight_club.flight_data import FlightData
 from flight_club.notification_manager import NotificationManager
 
@@ -89,3 +96,123 @@ def test_send_whatsapp_calls_pywhatkit_with_documented_arguments(
     monkeypatch.setitem(sys.modules, "pywhatkit", fake)
     assert NotificationManager().send_whatsapp("hello") is True
     assert received == [(NUMBER, "hello", 15, True, 3)]
+
+
+SMTP_HOST = "smtp.example.test"
+SENDER = "club@example.test"
+APP_PASSWORD = "app-password-secret"
+
+
+class FakeSMTP:
+    """Stands in for smtplib.SMTP; records what the manager does and sends nothing."""
+
+    instances: ClassVar[list["FakeSMTP"]] = []
+    fail_with: ClassVar[Exception | None] = None
+
+    def __init__(self, host: str, port: int) -> None:
+        if FakeSMTP.fail_with is not None:
+            raise FakeSMTP.fail_with
+        self.host = host
+        self.port = port
+        self.started_tls = False
+        self.login_args: tuple[str, str] | None = None
+        self.messages: list[Any] = []
+        FakeSMTP.instances.append(self)
+
+    def __enter__(self) -> Self:
+        return self
+
+    def __exit__(self, *args: object) -> None:
+        return None
+
+    def starttls(self) -> None:
+        self.started_tls = True
+
+    def login(self, user: str, password: str) -> None:
+        self.login_args = (user, password)
+
+    def send_message(self, message: Any) -> None:
+        self.messages.append(message)
+
+
+@pytest.fixture
+def smtp(monkeypatch: pytest.MonkeyPatch) -> type[FakeSMTP]:
+    FakeSMTP.instances = []
+    FakeSMTP.fail_with = None
+    monkeypatch.setenv(ENV_SMTP_ADDRESS, SMTP_HOST)
+    monkeypatch.setenv(ENV_EMAIL_ADDRESS, SENDER)
+    monkeypatch.setenv(ENV_EMAIL_PASSWORD, APP_PASSWORD)
+    monkeypatch.setattr(smtplib, "SMTP", FakeSMTP)
+    return FakeSMTP
+
+
+def test_send_emails_logs_in_and_sends_one_mail_per_address(smtp: type[FakeSMTP]) -> None:
+    sent = NotificationManager().send_emails(["a@example.test", "b@example.test"], "deal")
+    connection = smtp.instances[0]
+    assert sent == 2
+    assert (connection.host, connection.port) == (SMTP_HOST, SMTP_PORT)
+    assert connection.started_tls
+    assert connection.login_args == (SENDER, APP_PASSWORD)
+    assert [m["To"] for m in connection.messages] == ["a@example.test", "b@example.test"]
+    assert all(m["From"] == SENDER for m in connection.messages)
+    assert connection.messages[0].get_content().strip() == "deal"
+
+
+def test_send_emails_encodes_non_ascii_text_as_utf8(smtp: type[FakeSMTP]) -> None:
+    NotificationManager().send_emails(["a@example.test"], "Only £54 to Zürich")
+    message = smtp.instances[0].messages[0]
+    assert "£54 to Zürich" in message.get_content()
+    assert message.get_content_charset() == "utf-8"
+    assert "£54".encode() in message.as_bytes()
+
+
+def test_send_emails_without_recipients_does_not_connect(smtp: type[FakeSMTP]) -> None:
+    assert NotificationManager().send_emails([], "deal") == 0
+    assert smtp.instances == []
+
+
+@pytest.mark.parametrize("name", [ENV_SMTP_ADDRESS, ENV_EMAIL_ADDRESS, ENV_EMAIL_PASSWORD])
+def test_send_emails_prints_instead_when_a_setting_is_missing(
+    smtp: type[FakeSMTP],
+    monkeypatch: pytest.MonkeyPatch,
+    capsys: pytest.CaptureFixture[str],
+    name: str,
+) -> None:
+    monkeypatch.delenv(name)
+    assert NotificationManager().send_emails(["a@example.test"], "deal") == 0
+    output = capsys.readouterr().out
+    assert "deal" in output
+    assert name in output
+    assert smtp.instances == []
+
+
+def test_send_emails_never_raises_or_prints_the_login_when_smtp_fails(
+    smtp: type[FakeSMTP], capsys: pytest.CaptureFixture[str]
+) -> None:
+    smtp.fail_with = smtplib.SMTPAuthenticationError(535, f"bad login {APP_PASSWORD}".encode())
+    assert NotificationManager().send_emails(["a@example.test"], "deal") == 0
+    output = capsys.readouterr().out
+    assert "SMTPAuthenticationError" in output
+    assert APP_PASSWORD not in output
+
+
+def test_build_message_for_a_direct_flight_has_no_stopover_text() -> None:
+    assert "stopover" not in NotificationManager().build_message(_flight())
+
+
+@pytest.mark.parametrize(("stops", "text"), [(1, "1 stopover."), (2, "2 stopovers.")])
+def test_build_message_for_a_stopover_flight_says_how_many(stops: int, text: str) -> None:
+    flight = FlightData(540, "LHR", "DPS", "2026-10-25", "2027-04-20", stops)
+    message = NotificationManager().build_message(flight)
+    assert message.endswith(f"Flight has {text}")
+    assert message != NotificationManager().build_message(_flight())
+
+
+def test_messages_use_gbp_and_not_the_pound_sign() -> None:
+    flight = FlightData(540, "LHR", "DPS", "2026-10-25", "2027-04-20", 1)
+    for message in (
+        NotificationManager().build_message(flight),
+        NotificationManager().build_message(_flight()),
+    ):
+        assert "GBP" in message
+        assert "£" not in message