Reverse DNS (rDNS), also called a PTR record, is a DNS lookup that maps an IP address back to a hostname. It’s the “reverse” of normal DNS, which maps a hostname to an IP address.
Reverse DNS is widely used in email sending because mailbox providers want to confirm that the server sending an email looks legitimate and professionally configured.
How reverse DNS works (simple example)
- Forward DNS: mail.example.com → 203.0.113.10
- Reverse DNS (PTR): 203.0.113.10 → mail.example.com
Why rDNS matters for email deliverability
When your server sends email via SMTP, receiving providers often check whether the sending IP has a valid reverse DNS entry. A clean PTR record can help with:
- Trust signals (your server identity looks real and consistent)
- Better filtering outcomes (less suspicion = fewer blocks/throttling in some cases)
- Reducing “technical misconfiguration” flags
Reverse DNS alone won’t “guarantee inbox,” but it’s a common baseline requirement—especially when combined with proper authentication and good list hygiene.
Common rDNS problems
- No PTR record for the sending IP
- Generic PTR (e.g., a random ISP hostname that doesn’t match your sending identity)
- Mismatch: PTR points to a hostname that does not resolve back to the same IP (missing/incorrect A record)
Forward-confirmed reverse DNS (FCrDNS)
A best practice is forward-confirmed reverse DNS:
- The IP’s PTR points to a hostname, and
- That hostname’s A record points back to the same IP.
This “round-trip consistency” can help reduce suspicion in automated filters.
rDNS vs SPF/DKIM/DMARC
Reverse DNS is different from email authentication:
- rDNS (PTR): validates the server/IP identity at the infrastructure level.
- SPF/DKIM/DMARC: validates the domain and helps prevent spoofing/phishing.
For stronger trust signals, use rDNS alongside authentication and good sending practices. See: DMARC and DKIM.
How rDNS is managed (important)
PTR records are typically controlled by the owner of the IP block (your hosting provider or your SMTP relay provider), not by your website’s DNS host. If you use a third-party relay, they usually manage rDNS for you.
If you’re sending transactional emails, using a dedicated relay can simplify infrastructure settings. Learn more: What is an SMTP relay?
Related terms
Mailpro and reverse DNS
PTR records aligned, before you press send
Every Mailpro sending IP has a matching PTR record that aligns with its HELO and your SPF. One fewer reputation signal to chase — it is already set up.