> I have a postfix-3.2.6 system that acts as a mail server and > pop/imap using dovecot for a small domain. The problem is that > people are increasingly using it as a relay to a personal account, > such as Gmail and Yahoo.
perhaps i misunderstand they are sending email from gmail/yahoo addresses from your MTA? if so those will get blocked in many cases and marked as spam in many others for example with gmail: _dmarc.gmail.com. 596 IN TXT "v=DMARC1; p=none; sp=quarantine; rua=mailto:[email protected]"; gmail.com. 205 IN TXT "v=spf1 redirect=_spf.google.com" _spf.google.com. 176 IN TXT "v=spf1 include:_netblocks.google.com include:_netblocks2.google.com include:_netblocks3.google.com ~all" ... you MTA is not going to be included in any of those records, so you're MTA isn't a valid origin for @gmail.com and you're not going to be able to sign messages with a valid (dkim) signature either this is how spf/dmarc works there is in some sense nothing to fix, if you want to send as [email protected] you have to do it through a gmail smtp relay (which they provide)
