Gmail enforces bulk-sender rules: authentication, one-click unsubscribe, and spam-rate thresholds under 0.3% in Postmaster Tools.
What reverse DNS (PTR) records are#
A PTR record maps a sending IP address back to a hostname. Mailbox providers check that the PTR resolves and that the hostname's A record points back to the same IP (forward-confirmed reverse DNS).
Why it matters#
Gmail's sender guidelines require valid forward and reverse DNS. Missing or generic PTRs are a classic spam signal and cause outright rejections at many gateways.
Setting up reverse DNS (PTR) records for Gmail#
- Ask your hosting or ESP provider to set a PTR for each sending IP.
- Use a hostname under your domain (mail1.example.com) rather than the provider's generic name.
- Create the matching A record so forward and reverse agree.
- Use the same hostname in the SMTP HELO/EHLO banner.
How Gmail reports results#
Open a delivered test message in Gmail and view the original or headers. Look for Authentication-Results and any provider-specific verdict headers. Use the provider's sender dashboard for aggregate reputation.
Common mistakes#
- Generic PTRs like 203-0-113-10.provider.net.
- HELO names that do not match the PTR.
Frequently asked questions#
Can I set PTR records in my own DNS?
No. PTRs live in the IP owner's reverse zone. Your hosting provider or ESP sets them, though some offer self-service.
Does Gmail require reverse DNS (PTR) records?
Gmail enforces bulk-sender rules: authentication, one-click unsubscribe, and spam-rate thresholds under 0.3% in Postmaster Tools. Treat reverse DNS (PTR) records as required for any meaningful volume.