SMTP Submission is a variant of the SMTP protocol which has been adjusted to work well for programs which send messages they created themselves, rather than transmit messages written by others.
It isn't absolutely necessary to use SMTP submission. It's also possible to configure a plain SMTP server to do handle submission (sometimes that's actually simpler).
Archiveopteryx includes an SMTP submission server for accepting mail from Archiveopteryx users and forwarding it via a smarthost. The server includes all the features specified by the submission RFC, all the extensions specified by the Lemonade standard for mobile email, and a little more.
Most importantly, Archiveopteryx can check that senders only use permitted addresses in From, Sender, etc. The variable check-sender-addresses controls that.
Quite often both Archiveopteryx and the MTA supports submission, and you have to decide which one to use.
Most MTAs use the Unix authentication system, so users most have a Unix account in order to send mail, and must use that password. If you use Archiveopteryx, then mail submission uses the the same user names and passwords as IMAP.
Archiveopteryx supports the Lemonade extensions for mobile email, which most MTAs don't.
Archiveopteryx supports TLS in its default configuration, and can enforce the use of TLS using allow-plaintext-access. Most MTAs require manual configuration to support encryption for submission, and cannot enforce its use. (A VPN and firewall can do that, of course.)
The default configuration of Archiveopteryx is suitable for most small sites. You may want to change smarthost-address to use a different mail smarthost.
The configuration file has many more relevant variables.
In case of questions, please write to email@example.com.
Last modified: 2010-11-19