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Reverse DNS (PTR) records and why mail servers care
What reverse DNS / PTR records are, how forward confirmation works, and how to look them up for free.
Forward DNS maps a hostname to an IP (A/AAAA). Reverse DNS maps an IP back to a hostname via a PTR record. Many mail systems expect the sending IP’s PTR to exist and to forward-resolve to the same IP — sometimes called FCrDNS.
Why it matters for email
Missing or mismatched PTR records are a common reason for deferrals and spam scoring. Hosting providers usually control PTR for the IPs they assign; you request the hostname you want (for example mail.example.com).
Lookup PTR →
Free via public DNS — includes forward confirmation when possible.
Also check reputation
PTR is necessary but not sufficient. Scan DNSBLs if delivery suddenly fails, and keep SPF/DMARC aligned with the same sending hosts.