MTA bouncing valid email addresses as "undeliverable"
I was having some bad issues with spam. It was recommended that I check the following boxes in zimbraAdmin:
I also added RBLs for:
Spam stopped being a problem, BUT now we've little by little started bouncing valid vendors emails as "undeliverable"
This is a HUGE problem. So far its only about a dozen addresses, but seems to be growing quickly (only 6 last week).
using one of the problem email addresses ( email@example.com), I've grep'd through logs and found:
Jan 8 09:10:15 mail postfix/smtpd: NOQUEUE: reject: RCPT from host-69-95-11-35.roc.choiceone.net[184.108.40.206]: 450 4.7.1 <CBSERVER.CBDOMAIN.local>: Helo command rejected: Host not found; from=<firstname.lastname@example.org> to=<email@example.com> proto=ESMTP helo=<CBSERVER.CBDOMAIN.local>
Which appears several times for each attempt they've made to try again.
I've added the following rule to the /opt/zimbra/conf/salocal.cf.in:
But it did not seem to affect the issue.
Is there a way to remedy this without turning off the reject rules? Hopefully one that does not require adding each domain to a safe list as I'm sure this problem will be reoccurring as time goes forward.
I need to get this figured out immediately, very large bids are being held up and we are risking loosing large accounts over it.
Thanks in advance for any help!