- Send from domain IP addresses and use domain names in SMTP greeting option is enabled in Tools & Settings > Mail Server Settings
- SMTP greeting contains the server hostname only
- The following record might be found in
postfix/smtp: 4F7921800D93: to=<[email protected]>, relay=mail.example.com[203.0.113.2]:25, delay=306940, delays=306940/0.07/0.14/0, dsn=4.4.2, status=deferred (lost connection with mail.example.com[203.0.113.2] while performing the HELO handshake)
- Online tool mxtoolbox.com shows the following:
Reverse DNS does not match SMTP Banner
- There is no PTR record for domain:
# dig PTR example.com
;; QUESTION SECTION:
;example.com. IN PTR
;; AUTHORITY SECTION:
example.com. 7931 IN SOA ns02.hostname.com. hort.hostname.com. 1511348154 10800 3600 604800 10800
PTR record is not configured for the domain.
Contact ISP to setup a reverse (PTR) record that matches the hostname of mail server.