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Is it possible to configure SMTP authentication on Postfix with different user/pass credentials for different domains?

So, I have a MTA that relays emails from ~20 different domains. When sending emails to a specific domain, say example.com, my MTA has to authenticate. No problem, this solved the problem: http://postfix.state-of-mind.de/patrick.koetter/smtpauth/smtp_auth_mailservers.html

But, I have a different account for every sender domain. So, when mydomain1.com sends email to example.com, it uses one account. Another one for mydomain2.com -> example.com etc.

Is this achievable through Postfix?

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You should read up a bit on this option: smtp_sender_dependent_authentication, with that, and two other related DB mappings, sender_dependent_relayhost_maps, and smtp_sasl_password_maps, you can create per sender password entries.

In the sender_dependent_relayhost maps, you map username@domain [smtp_host], and in the smtp_sasl_password maps, you map email user:password or domain user:password(whatever those might be). These are classic postfix lookup tables, they can be in mysql, dbm, hash, etc.

With a combination of mysql and some duplication, you could quite possibly do what you want.

You could make a table with 4 fields, email, smtp_relay, user, password, then have postfix look up the email and smtp_relay for the sender_dependent_relay_maps, then email user:password for smtp_sasl_password_maps. This would have to be populated with each email address that has to relay, each server that you relay through, and each user:password combo for the authentication.

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    Very good answer,but you could have linked the official SOHO configuration readme ;-) postfix.org/SOHO_README.html#client_sasl_sender – Stefan Förster Jan 8 '14 at 6:58
  • @StefanFörster Yeah, but I wanted to explain the slightly different logic you would have to use to solve his situation, as not only does he have multiple relays, but each from domain needs a different account to send with.. it feels a bit cheap to write look at this, but change here, here and here :) – NickW Jan 8 '14 at 9:10
  • @NickW -- thanks for the answer. Could wildcards be used? Like, *@mydomain1.com, *@mydomain2.com etc. Because there are hundreds of mail addresses and dozens of domains. Only one destination mail server. User accounts on destination servers are 1:1 for domain:account. Users need to authenticate *only when sending emails to a single exact mail server. When sending to other mail addresses, no need for authentication. – kreso Jan 8 '14 at 10:13
  • As far as I know, you should be able to use them, have a look at the pcre: maps.. postfix.org/pcre_table.5.html – NickW Jan 8 '14 at 10:25
  • This probably isn't what I'm looking for. If I'm not mistaken, sender_dependent_relayhost_maps would just say that all emails from sender@domain1.com are being relayed to smtp_host. What I'd need is, if there is mail from ANY_USER@domain1.com, being sent to smtphost.address.com, then authenticate using account domain1.com|password1. All other emails should just be relayed based on MX records. – kreso Jan 8 '14 at 10:26

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