Using zimbra on Centos 5, I can receive emails correctly but if I try to send emails to hotmail, yahoo, you name it...i instantly get a bounced email with this info:
This is the Postfix program at host mail.goldenpartners.com.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to <postmaster>
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The Postfix program
<firstname.lastname@example.org>: host ptysystems.com[18.104.22.168] said: 550 5.1.1
<email@example.com>... User unknown (in reply to RCPT TO command)
Im using a zimbra account called firstname.lastname@example.org that can receive all kinds of emails, and then im using this acccount via zimbra web interface to send a test email to any kind of external email (internal works fine).
My DNS are all ok.
maybe something is messed up in postfix.