Advertise available addresses to MTA

[EtienneBruines]

Let's say we have one e-mail account [email protected]. If we want to store e-mail from this e-mail address, we should configure the MTA (Postfix in this example) to receive this e-mail, and forward it to our IMAP server.

If it forwards it to the IMAP server, the IMAP server can say "OK, received", or something like "NO, I don't know that user". In the latter case, the MTA often tries to send an Undelivered Mail Returned to Sender e-mail to the sender-address (which does not have to be the actual sender). This causes backscatter.

So, we should tell the MTA which e-mails should be forwarded, and which e-mails should not.

Possibilities

• [ ] Using Unix sockets (socketmap_table) - I want to support at least this
• [ ] Using TCP sockets (tcp_table)
• [x] Using DBMS systems (nothing to support; when we can read from MySQL, then so can Postfix)
• [ ] Support anything else than Postfix (exim4, ...?) -- help wanted

... more?

This issue is there for discussion / new possibilities to implement.