It's possible, but it's presently a hassle to configure for.

so the catchall should not redirect mail for existing users.

• luser_relay = [email protected]
  • The local delivery agent is for the DMS hostname (eg: mail.example.com), usually system mail / notifications.
  • This should be to a valid mailbox, in DMS use setup email add for example, or a remote mail address.
• @example.com [email protected] at the end of your postfix-virtual.cf file.

  • This file is typically managed via our setup alias ... commands. You can edit it directly.

  • It must come after any earlier virtual aliases, as the first successful match takes precedence.

  • When postfix-virtual.cf is updated (unless using LDAP at present), it should be processed and a copy made to /etc/postfix/virtual. This matches the Postfix config:
    virtual_alias_maps = texthash:/etc/postfix/virtual

  • Alternatively, you can provide your own additional texthash:/path/to/file lookup table to the virtual_alias_maps setting. This will ensure it's always checked after the first file, allowing you to use setup alias ... commands without that sort order concern.

    To do this, you can use our postfix-main.cf override file support, and include the updated setting. For example if we add alias-catch-all.cf as a new file to our DMS config volume:
    virtual_alias_maps = texthash:/etc/postfix/virtual, texthash:/tmp/docker-mailserver/alias-catch-all.cf
    Then start your container (postfix-main.cf does not attempt to update automatically, it's only run during container startup), and your catch-all should be working.

NOTE:

• The virtual aliases should also apply to local before it resolves it's own internal/local-only /etc/aliases table.
• Virtual aliases can resolve recipient for outbound mail too IIRC, this is more of an issue when using the similar support for a virtual alias regexp config if the pattern is too relaxed.
• There is a known problem (with tracking issue).
  • Virtual aliases resolve before virtual mailboxes (Dovecot managed, these are what DMS accounts are using via postfix-accounts.cf).
  • A catchall will be the fallback when no other virtual alias matches. Now your DMS accounts never receive mail as the catchall was hit before they got a chance. The workaround is to redundantly create an explicit alias for each DMS account.
  • However setup alias add no longer supports a virtual alias that overlaps with a DMS account, as that has caused problems in the past for some users (misuse), so this requires manual management similar to the catchall advice/gotcha described for postfix-virtual.cf.