Hello!

I have a working Postfix/Dovecot setup with virtual domains and users in a mySQL database.

Problem:

I need to do some rewriting of the sender addresses of outgoing mail according to this general rule/pseudocode:

IF
(user=MYVIRTUALUSER@mydomain.address) AND
(Subject.Field.Contains.The.String = "send.as.barbara")
THEN:
Swap all instances of "From: MYVIRTUALUSER@mydomain.address" to
"From: barbara@other.domain.address"

What this is meant to accomplish:

When I use a remote mail client, I can choose sender identity based on the content of the Subject: field.

If no special string is put into Subject:, then the mail is left unchanged (From: MYVIRTUALUSER@mydomain.address).

If a special string "send.as.x" is put into Subject:, then the filter script changes From: fields, so that Postfix relays the mail to predefined (authenticated) SMTP servers by use of sender_dependent_relayhost_maps.

This makes possible "server side identity management" for the case that I use a really stupid (!) mail client with no identity management of its own, and that can use only 1 SMTP server.

What I've tried so far:

Nothing!

I was thinking I could use 'procmail' to do this, but it seems that it can only act on /incoming/ mail, not outgoing.

The built-in Postfix address rewriting features don't seem to be flexible enough to do rewriting based on a regex in specific fields (or anywhere).

My question:

What can I use to rewrite Sender address according to the rule above? A shell script? How do I make Postfix filter outgoing mail through it?

EDIT:
This page http://www.debianadmin.com/how-to-ad...n-postfix.html looks close to what I want to do! Seems to use the "dfilt" pipe?

You can do one of two things:

• Enable postfix after-queue content filters (http://www.postfix.org/FILTER_README.html)
• Add a new transport mechanism to your master.cf

The new transport can be something like:

1 members found this post helpful.

Aha!

"After-queue content filters" looks simple enough and would probably allow some exotic manupilation.

(Hoping that performance won't suffer too much...)

Thank you!

Salantrax, did you managed to find a way to do this?
I kind of need to do the same as well.. thank you

The solution was given above, in post #2. Either enable after-queue processing, or a new transport script, as noted.

Hi TB0ne,

I did try the after queue filters, but it did not work out. Let me explain:

I have ssmtp installed so that sendmail sends everything out as abc@gmail.com
I'm not sure how my postfix works, but it is handling other domains correctly.

this is how my relayhost_map looks like

@example.com [example.com]:25
@hotmail.com [smtp.live.com]:25
@gmail.com [smtp.gmail.com]:587

when I followed the 30 line shell script on http://www.postfix.org/FILTER_README.html and send a test mail from abc@example.com, it was always received as abc@gmail.com, not abc@example.com

Basically, sendmail is behaving the way I want it to, however the script relies on sendmail to pass filtered content back to postfix. I have no idea how to overcome this. Any help is greatly appreciated.

As for the new transport, your previous example is too terse for me to understand. I did try googling, but gave up. Main trouble is not knowing how the script is supposed to handle inputs from and output returns to postfix.

As my mail server is handling live emails, I was hoping for a more walk-through example, rather than experimentation that may break something.

Any pointers will be greatly appreciated! (btw I'm conversant in php, that's what i'm hoping to write the script in) Thank you!