smtp return address rewriting

Question

I work for a small company that has a simple customer service system. We have a single email address, [email protected], and a program that forwards that mail on depending on the inbound address. For instance, If we have two employees, Adam and Ben, they each have an email address, [email protected] and [email protected]. Adam has certain clients he deals with, ben has certain clients he deals with, and any emails from unknown addresses goes to a [email protected] address.

This side of things works fine. However, when they reply to a customer, the customer sees a return email from [email protected] rather than [email protected]. This is what I want to fix.

What possible solutions are there, without touching the mail clients of Adam or Ben? Is it possible to do something to the emails at the point when my program routes them from the support mailbox to one of the individual mail boxes? Is there any kind of header parameter, or similar, that might allow this?

I thought about setting the return address so that the incoming address is masked from adam or ben: so that when they reply, it sends a mail to [email protected], and then by keeping track of conversations and so on I could forward the mail on to the correct recipient... but this seems needlessly complicated. Is there a better solution?

Answer 1

If Adam and Ben always send replies via your mail submission server, you could just rewrite the sender address there before relaying to the client.

If Adam or Ben use their own outgoing SMTP server to send replies, you have more trouble. Your best bet in that case would be to use something along the lines of SRS to rewrite the sender's address before forwarding on to Adam or Ben. Then when Adam or Ben replies it will come into your system, at which point you can un-SRS and rewrite the sender to [email protected] before forwarding it on to the client's actual address.

Answer 2

Maybe set the "Reply to:" mail header line ?

Answer 3

There's a standard called Sender Rewriting Scheme (SRS) that does something similar in the context of Sender Policy Framework (SPF), which performs authentication of the domain name of the sender.

However, for practical purposes, what you want to do, together with your requirements of not having to modify the settings on the Mail User Agent side, have limited utility — if you rewrite every single email from any employee to have a support@ prefix, then this kind of defeats the purpose of them not simply configuring their clients to have support@ as the outgoing email.

The best solution would be to use the alias features of the email clients, such that the MUA could automatically use the [email protected] email address if it sees that the email was originally sent to [email protected] instead of personally to any individual employee. This feature is called alternates in mutt, for example.