King0770-Notes-MTA-ALLOW-HELO
One occasion external domains may not have valid resolvable hostnames for their helo-hostname; would see something like this.
mail.example.com #4.4.7 SMTP; 450 4.7.1 <srv004.xxxyyy8.com>: Helo command rejected: Host not found>
Update the MTA Config
Update the smtpd_recipient_restrictions.cf File
Edit the /opt/zimbra/conf/zmconfigd/smtpd_recipient_restrictions.cf file, and at very top of the file, add the following.
%%contains VAR:zimbraMtaRestriction check_helo_access lmdb:/opt/zimbra/conf/allow_helo%%
Create the allow_helo file
Run the following as the zimbra user (not root)
touch /opt/zimbra/conf/allow_helo
postmap /opt/zimbra/conf/allow_helo
Pick Up the Changes
zmconfigdctl restart
zmmtactl restart
Check it
zmprov -l gacf zimbraMtaRestriction | grep check_helo_access
zimbraMtaRestriction: check_helo_access lmdb:/opt/zimbra/conf/allow_helo <<== You should see this
postconf | grep ^smtpd_recipient_restrictions
smtpd_recipient_restrictions = check_helo_access lmdb:/opt/zimbra/conf/allow_helo <<== You should see this
Add entry to /opt/zimbra/conf/allow_helo file
srv004.xxxyyy8.com OK
After updating /opt/zimbra/conf/allow_helo, run postmap against it.
postmap /opt/zimbra/conf/allow_helo
More articles written by me, https://wiki.zimbra.com/wiki/King0770-Notes