How do I connect Apple Mail, Outlook or Thunderbird?

Other mail apps connect over IMAP with an app password, which you create in Settings → App passwords. Create one per app per device, so losing a laptop costs you one password rather than all of them.

Two things people get wrong:

• The username is your full email address, not the part before the @. The short form is refused, and the refusal looks exactly like a wrong password.

• The app password is shown once. It cannot be retrieved afterwards. If you did not save it, revoke it and make another — that is cheaper than it sounds.

Calendars and contacts connect the same way, over CalDAV and CardDAV.