Reverse DNS (PTR) Lookup
Find the hostname behind a sending IP and check that it resolves back to the same IP (forward-confirmed reverse DNS).
How it works
Receiving servers look up the PTR record of the connecting IP. Missing or mismatched reverse DNS is one of the fastest ways to get mail rejected, particularly by Gmail and Microsoft.
PTR records are set by whoever owns the IP - usually your hosting or cloud provider, not your DNS registrar.
Automate it with the API
Run this check for every address in your product, from any language.
curl -X POST "https://www.mailrambo.com/v1/verify?detail=full" \
-H "Authorization: Bearer $MAILRAMBO_KEY" \
-H "Content-Type: application/json" \
-d '{"email": "jane@acme.com"}'
# -> detail.dns: { spf, dmarc_policy, dkim_selectors, bimi, ptr, mx_hosts }API reference · Get a free API key
Frequently asked questions
Who sets my PTR record?
The owner of the IP block: your VPS, cloud or email provider. Look for 'reverse DNS' in their control panel or ask support.
What is forward-confirmed reverse DNS?
The PTR hostname resolves back to the same IP. Receivers treat an unconfirmed PTR almost like a missing one.
Related tools
MX Record Lookup
See a domain's mail servers, priorities and email provider.
Email Domain Health Checker
Full deliverability report: MX, SPF, DKIM, DMARC, BIMI and PTR with an A-F grade.
DNS Records Lookup
A, AAAA, MX, NS, TXT, CNAME, SOA and CAA records in one view.
SPF Record Checker
Validate SPF and count DNS lookups against the 10-lookup limit.
Run these checks from your code
Verify addresses at signup, clean lists and read SPF/DKIM/DMARC with one API call. 100 free verifications a month, test keys that cost nothing, and the API on every plan.