On Thu, 12 Sep 2019 at 10:24, Chris Wedgwood <[email protected]> wrote: > > > 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
but note in the DMARC record that you quote: ' p=none': Gmail is telling other servers *not* to block (or quarantine) emails from @gmail.com that do not obey SPF or DKIM rules. Yahoo by contrast: # dig +short _dmarc.yahoo.com TXT "v=DMARC1; p=reject; pct=100; rua=mailto:[email protected];";
