SMTP greeting contains the hostname only: lost connection while performing the HELO handshake

Dmitry Bystrov

10 months ago

Symptoms

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 /var/log/maillog file:
postfix/smtp[30864]: 4F7921800D93: to=<john.doe@example.com>, 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.

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