Setting up a relay mail server that stores all e-mail for resending purposes?

Question

Previously I was the owner of a Barracuda Spam Firewall and the backlog had helped me many times. It offers a lovely view of all e-mail that has passed the server and even allows for resending those e-mails.

I know e-mail is not supposed to work this way, but it's a great selling point, so users will never lose their e-mail, even when their mailserver would be down and failure notices had to be sent, they could still request a resending of e-mails to their domain.

I am looking for a way to resend all e-mails sent in the last 2 days to a specific domain. Can postfix help with this? Any recommendations in realizing such a construction would be welcome!

Answer 1

I'm actively developing this feature for our (sadly, non-free) postfix-based application, so I have some good experience with what postfix can and cannot do in this arena. Unfortunately, the list of cannot-do's is longer than the list of can-do's.

Postfix alone won't really do what you want. You'll almost certainly need to do some hacking of your own (or find a third party app that extends a standard MTA, as suggested by the first answer).

The approach we're taking is to deliver the message to two recipients--the intended original recipient, as well as a local version of the same recipient (for instance user_domain.com@localhost). Then if/when mail needs to be resent, we can re-send it from the local mail store. Of course, it's rather complicated to set all this up, and to automate the resending feature. Also, I have not found a reasonable way to handle the two-address aspect in postfix itself--we have another script running in front of postfix on port 25 that mangles the addresses (and does much, much more, well beyond the scope of this question). So by the time postfix sees the message, it already has two addresses.

Answer 2

You might take a look at ESVA (http://sourceforge.net/projects/esva-project/). It seems that the project may have died off, but its functionality that meets your requirements are very stable.