AI Email Filter can sort a reachable, supported IMAP mailbox without changing its MX records or replacing your email client. Fastmail, Posteo and mailbox.org do not have one identical password policy. Check your account’s access settings before connecting.
Start with the provider’s IMAP settings
| Provider | IMAP host | TLS port |
|---|---|---|
| Fastmail | imap.fastmail.com | 993 |
| Posteo | posteo.de | 993 |
| mailbox.org | imap.mailbox.org | 993 |
Use your account’s login address, not an assumed alias. Confirm current settings in the provider’s documentation and make sure external IMAP access is permitted. The mail-sorting connection is IMAP; you do not need to configure your account’s SMTP server to connect it.
Fastmail
Fastmail requires an app password with mail access for third-party clients; its Basic plan does not include IMAP. See app passwords and server settings.
Posteo
Do not assume an app password is mandatory on every Posteo account. Verify the enabled mailbox protections and their authentication requirements in Posteo’s help center. If external access is disabled, an otherwise correct password will not establish an IMAP connection. We have not independently completed a Posteo account connection test for this article.
mailbox.org
Use the provider’s Email app-passwords instructions, which distinguish mail access from other application passwords. Verify IMAP permission and your current two-factor authentication configuration in mailbox.org’s official guide.
Separate connection errors from sorting errors
An authentication error means you should check the login, password type and permitted access. A timeout points toward reachability or provider availability. A successful connection followed by an unexpected category needs a prompt and classification review, not different MX records.
Once connected, create a single category and use a dry preview before applying folder moves. Test a legitimate message and a similar message that should be excluded. Keep the original messages available in your mail client for comparison.
Keep the privacy boundary clear
The application processes message data even if your mailbox remains at a privacy-focused host. A custom model can have a configured default-provider fallback; sender caching is conditional. See IMAP setup, sender categories and private sorting.