Hi.
I've noticed that Aqua mail appears to have a small but irritating non-compliance with RFC 5321.
When testing the server configuration by logging in and testing sending of email to the SMTP server, Aqua mail sends a non-compliant "MAIL FROM:" command. The command is sent in the form "MAIL FROM: <user@example.com>" rather than in the compliant form of "MAIL FROM:<user@example.com>"; i.e. there is a space between the "FROM:" and the reverse path. It may do this when actually sending emails as well - I couldn't get that far :-)
This means that Aqua mail is unable to validate against a dovecot/submission server unless that server is specifically configured to handle this type of broken behaviour. By default, dovecot will respond with a 501 error "Invalid FROM: Unexpected whitespace before path" unless it has been configured with "submission_client_workarounds = whitespace-before-path".