I have acquired a number of mail users, and I'm wanting to transition them away from their current mail server and onto mine. I've set up perdition as a proxy which will allow me to proxy IMAP and POP connections - and I have control of the DNS used to direct them to the appropriate mail server. I do not have access to the old mail server.
The mail proxy server is running Linux
Unfortunately I suspect a lot of people are using the same server for POP3 and SMTP.
I am wanting to set up an SMTP proxy so I can seemlessly provide SMTP services to the customers during the transition - without an open mail relay. It does not appear that Perdition offers this solution natively.
Is anyone aware of a solution which either proxies SMTP requests (including AUTH requests) - ideally with the ability to map which requests go to which backend ? [ I've not tried an IPTables DNAT rule - I suspect this might work, but I loose the ability to do authentication to different servers on a per domain / client basis, which makes migration substantially harder ].
I have tried configuring Dovecot as a director / proxy in place of Perdition. This works fine for IMAP and POP, but not for SMTP - Specifically it will authenticate based on username or domain name - it does not check the actual credentials against the SMTP server.