Postfix client-side smtp auth. (sasl) against one relay host for multiple users
my local Postfix server relays any incoming mail to the ISP's mailserver. That relayserver requires smtp-authentication, so i built the sasldb2.db with "mailserver.isp.com email@example.com:Password" to do do. That works for one mailaccount.
The Postfix manual says that you can define different relayhosts with different login each (mail.isp1.com login:Passwd / mail.isp2.org login:Passwd etc.)
BUT now i have multiple Users to authenticate against one relayhost. Postfix does not know which login/pw to use when he has to authenticate. And the relay won't accept a mail from authenticated user1 when there is a user2 in the 'mail from:'.
Is my Postfix server not able to parse the 'mail from:' line and use this for a lookup on an sasl-login-table or something like that.
How can I solve this problem?