Definition
Normal DNS lookups turn a hostname into an IP address. A PTR (pointer) record does the reverse: it turns an IP address into a hostname. This is called reverse DNS, or rDNS.
PTR records live in special zones (in-addr.arpa for IPv4, ip6.arpa for IPv6) and are controlled by whoever owns the IP address, usually your hosting provider or email service, not your domain's DNS host.
Mail servers often check that forward and reverse DNS agree:
- The connecting IP has a PTR record pointing to a hostname, for example
mail.example.com. - That hostname resolves back to the same IP.
This is known as forward-confirmed reverse DNS.
Why it matters
A sending IP with no PTR record, or one with a generic name that looks like a home connection, looks suspicious to receiving servers. Many will filter or refuse its mail.
Google's sender guidelines, in force since February 2024, require every sender to Gmail to have valid forward and reverse DNS records for their sending IPs. Yahoo's guidance is similar.
If you send through a mainstream email platform or Google Workspace or Microsoft 365, reverse DNS is handled for you. It becomes your job when you run your own mail server or rent dedicated IPs.
How SimpleCold handles it
PTR records describe the sending side, so they do not change whether a recipient's address is valid. SimpleCold verifies recipients. If you run your own infrastructure, check reverse DNS alongside SPF, DKIM and DMARC before you send. The free blacklist checker is a useful companion for checking whether a sending IP is listed.