Upgrade to 7.2 broke external Mail Relay

[Tyre77]

I just upgraded from 7.1 to 7.2 and unfortunately it broke my external mail relay (was working perfectly before this). Now when I try to send an email I get the following bounce back:

This is the mail system at host zimbra.*****.org.

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 mail system

<******@gmail.com>: host smtp.sasktel.net[69.49.109.87] said: 550 5.7.1
<******@gmail.com>... Relaying denied: You must check for new mail before
sending mail. (in reply to RCPT TO command)

I've tried installing pop-before-smtp but either I don't have it configured right or it's not working.
Any help would be greatly appreciated.

*** UPDATE ***

I copied all the files from /opt/zimbra/postfix-2.7.4.2z to /opt/zimbra/postfix-2.7.8.3z and restarted zimbra and now I'm able to send email again. Not sure what in the new postfix isn't working quite right though.

[Tripple]

Take a look at /opt/zimbra/postfix/conf/main.cf .

[Tyre77]

Take a look at /opt/zimbra/postfix/conf/main.cf .

Unfortunately I'm not 100% sure what I would be looking for in there?

[Tripple]

Maybe you could compare main.cf from /opt/zimbra/postfix-2.7.4.2z with /opt/zimbra/postfix-2.7.8.3z.

I'm not sure what you're trying to achieve, but if you want to relay a domain, maybe there's a line in /opt/zimbra/postfix/conf/main.cf that looks like this:
relay_domains = $mydestination, your_relay_domain.com

I doubt however that's what you want, maybe you could give some more details.

[Tyre77]

Maybe you could compare main.cf from /opt/zimbra/postfix-2.7.4.2z with /opt/zimbra/postfix-2.7.8.3z.

I'm not sure what you're trying to achieve, but if you want to relay a domain, maybe there's a line in /opt/zimbra/postfix/conf/main.cf that looks like this:
relay_domains = $mydestination, your_relay_domain.com

I doubt however that's what you want, maybe you could give some more details.

I did a diff of the two files and there were several lines pertaining to my ISP's mail servers that I use for relaying missing out of the new main.cf. I copied the differences over, restarted zimbra and it's working now.

Thank you so much for your help, it's really appreciated.