Reverse DNS, PTR and HELO: establish the sending server identity

Receiving systems expect the delivering server to present a stable hostname with coherent forward and reverse DNS. Missing or generic identity weakens trust.

During delivery, a mail server announces a hostname using HELO or EHLO. The receiving system can compare that name with the source IP's reverse-DNS PTR record and then resolve the hostname back to an address.

Sending IP: 203.0.113.25
PTR: mail.example.com
A/AAAA: mail.example.com → 203.0.113.25
HELO/EHLO: mail.example.com

Perfect one-to-one matching is not the only valid architecture, but the names must be real, resolvable and operated consistently. Generic residential hostnames, missing PTR records and names that do not resolve are common warning signs.

What AuthSMTP manages

When AuthSMTP delivers a message, our infrastructure supplies the delivery IP, reverse DNS and SMTP server identity. Customers should not publish PTR records for AuthSMTP IPs. Your responsibility is the message and domain authentication layered above that transport.

Send a normal message to AuthEmailTest.com to inspect the server identity actually seen by a recipient.

Key takeaway
Ensure the sending IP, PTR, forward DNS and SMTP HELO/EHLO name describe the same stable server identity.
Practical next step

Inspect the Received headers of a delivered AuthSMTP message and confirm that the visible transport identity is coherent; contact support with the complete headers if it is not.

Using AuthSMTP

AuthSMTP manages the PTR, forward DNS and SMTP identity of its delivery servers. Customers should authenticate their visible sending domains rather than attempting to configure AuthSMTP transport IPs.