According to you SPF, you are allowing any host (A record in the DNS) to
send messages.
I think you should limit your Domain to your genuine email servers only, and
not allow any server in your farm to send messages while clients (other
domains) include your SPF.
However, I'm a bit confused why servers server{1..20}.cretaforce.gr have
MTAs and are all allowed by SPF.
Overall, the config looks too opened and anyone hacking your clients can do
mass mailing. http://akrogiali-restaurant.gr/ seems to be hacked, and
backlisted which means their messages will go to Spam folder.
-----Original Message-----
From: owner-postfix-us...@postfix.org
[mailto:owner-postfix-us...@postfix.org] On Behalf Of Christos Chatzaras
Sent: Sunday, May 24, 2015 2:48 PM
To: postfix-users@postfix.org
Subject: Re: problem with spam
We have some customers that use their gmail account for SMTP, but on port
587 and not port 25. So I don't think it will cause any problem. If it cause
any problem I can enable smtp to port 25 for specific customers.
