What it is
Reverse DNS maps a sending IP to a hostname. Forward-confirmed reverse DNS means that hostname resolves back to the IP.
Why it matters
Mailbox providers expect accountable infrastructure. Missing or generic identity is a common rejection and reputation signal.
How to implement
Assign a dedicated, meaningful hostname to each sending IP, configure PTR through the IP owner, publish matching A or AAAA records, and use that hostname in SMTP EHLO.
Common mistakes
- Setting a PTR that does not resolve forward.
- Sharing one hostname between unrelated operators.
- Greeting with
localhostor a bare IP literal.
Verification
Resolve IP → PTR → address and compare the SMTP banner and EHLO name. Repeat from a resolver outside your own network.