Email messages sent from webmail, but not received on recipient (Gmail, Yahoo, etc)
I have this really annoying problem: when I send emails from Thunderbird (SMTP/POP3) to external email addresses (not from sites hosted on the server), everything works just fine, but when I try to send from the web interface (squirrelmail, roundcubemail), the message is reported as "Sent successfuly", but the recipients never receive it. I have spent 2 days on this, and I don't want to waste any more time. Please help!
I have Ubuntu Server 9.10 32bit with Perfect Setup, I am using a commercial DynDNS hosted domain (let's call it "xyz.com").
My server host is "server1.xyz.com".
I think that there's something in the headers of the email being sent that makes recipient mail agents think it's spam, or incorrect, or "bad". I may be wrong. That's why I am asking for help here.
Please let me know what log files / output to list here.