Is the return address valid (i.e., will your server accept mail sent to
sales@myserver.org)? Many receiving mail servers check to see if the address sending mail is valid before accepting mail from it.
Best thing to do is probably to tail your mail log while sending a message from sales@ and see what the discussion with the gmail server looks like in real time.
Code:
tail -f /var/log/mail.log
(or whatever your mail log file is).
Here's what a successful transaction looks like from Postfix:
Code:
Sep 10 08:10:36 brightstar postfix/pickup[28133]: 35A46141C5: uid=1000 from=<username>
Sep 10 08:10:36 brightstar postfix/cleanup[28675]: 35A46141C5: warning: header Subject: Test from local; from=<username@myserver>
Sep 10 08:10:36 brightstar postfix/cleanup[28675]: 35A46141C5: message-id=<20130910151036.35A46141C5@myserver>
Sep 10 08:10:36 brightstar postfix/qmgr[27663]: 35A46141C5: from=<username@myserver>, size=376, nrcpt=1 (queue active)
Sep 10 08:10:37 brightstar postfix/smtp[28715]: 35A46141C5: to=<username@gmail.com>, relay=gmail-smtp-in.l.google.com[74.125.129.27]:25, delay=0.93, delays=0.01/0.01/0.22/0.7, dsn=2.0.0, status=sent (250 2.0.0 OK 1378825837 sl4si17533021pac.184 - gsmtp)
Sep 10 08:10:37 brightstar postfix/qmgr[27663]: 35A46141C5: removed
The second to last line, where it says "250 2.0.0 OK..." will reflect an error message of some kind if gmail is refusing your mail.