Task: connect T-Online account via IMAP (read-only proof of concept)

[Hohnik]

Part of MailChat MVP: email-as-chat spec

Question

Using the credential approach resolved by the T-Online app-password research ticket, connect to secureimap.t-online.de:993 over SSL using the credentials in src/mailchat/.env, and prove read access by fetching real messages (list folders, fetch a handful of message headers/bodies from INBOX).

Scope: IMAP read only — sending is a separate follow-up ticket.

Record what worked: the exact auth flow used, whether an app-specific password was needed (and how it was generated), and which Python library/approach was used to connect.

[Hohnik]

Answer

Confirmed working end-to-end against the real T-Online account.

Auth flow: standard IMAP login (imaplib.IMAP4_SSL.login(username, password)) against secureimap.t-online.de:993 (SSL). No OAuth, no special TOTP handling needed at the protocol level — per the earlier research ticket, T-Online requires the separately-generated "Passwort für E-Mail-Programme" in place of the regular account password; once that's in .env, plain IMAP LOGIN works.

App-specific password: yes, needed (confirmed — see #2). The regular account password does not authenticate.

Library/approach: Python stdlib imaplib only — no third-party IMAP library needed. Implemented as src/mailchat/sync/imap_client.py:

• ImapCredentials — plain dataclass (host/port/username/password), intentionally not tied to any config-loading mechanism, so the module stays a clean, testable low-level wrapper
• connect() — context manager: login on enter, logout on exit (even on exception)
• list_folders() — wraps IMAP4_SSL.list()
• fetch_recent_messages() — read-only SELECT, SEARCH ALL, FETCH ... (RFC822), returns raw message bytes (parsing into structured messages is sync/parser.py's job, not this module's — kept the boundary clean)

Tests: tests/test_sync/test_imap_client.py, 6 unit tests against a mocked imaplib.IMAP4_SSL (connect/login/logout lifecycle, folder listing, message fetch, error paths). All passing. Per the map's testing note, the real T-Online account was used only for this one-off live proof, not wired into the permanent automated suite.

Live proof: connected to the real account, listed 10 folders, fetched 3 recent INBOX messages read-only. Real subject lines observed confirm the German prefix pattern the grouping-model ticket (#5) will need to handle, e.g. "DL-4916597: Re: Re: Kundennummer 0008495381" (double Re: prefix).

Project plumbing added as a prerequisite (repo had no working test setup at all): pyproject.toml now has a [build-system] (hatchling) and a pytest dev dependency group; src/mailchat/sync/__init__.py was added (was missing, unlike sibling modules); uv sync sets up .venv against Python 3.13.

Not yet committed to git — left for review.

[Hohnik]

Resolved — see comment above.