About reverse DNS
A PTR record maps an IP back to a hostname. Mail servers expect the sending IP to have a PTR that resolves forward to the same IP (FCrDNS). Missing or generic PTRs (like ISP pool names) are a strong spam signal. Set the PTR through whoever owns the IP, usually your hosting provider.
Reverse DNS (PTR) check: questions
What is a PTR record used for in email?+
It maps the sending server's IP address back to a hostname, which receivers check before trusting the connection. Many reject or penalise mail from an IP that has no PTR record, or one that does not resolve back to the same IP, and Gmail's sender guidelines require valid forward and reverse DNS for sending IPs.
How do I set up a PTR record for my mail server?+
Through whoever controls the IP address, usually your hosting or cloud provider: PTR records live in the provider's reverse DNS zone, not in your domain's DNS, so set it in their control panel or ask their support. Point it to a hostname such as mail.example.com whose A or AAAA record returns the same IP, ideally the name your server uses in HELO.
What is forward-confirmed reverse DNS?+
A PTR record whose hostname resolves back to the same IP address. Checking it takes two lookups: IP to hostname through the PTR record, then hostname to addresses through A or AAAA. If the original IP is among those addresses, the reverse DNS is forward-confirmed (FCrDNS). This check tests exactly that, for IPv4 and IPv6 addresses.
Does the PTR hostname have to match my domain?+
No. It has to exist and resolve back to the same IP, and a hostname under your provider's domain is fine. What hurts is a generic name that embeds the IP address or words such as dynamic or pool, which looks like a home connection; the check flags those. Matching the hostname your server announces in HELO is good practice.
Do I need a PTR record if I use Google Workspace or Microsoft 365?+
No. Their sending IPs already have PTR records that the provider manages, as do the shared IPs of email services such as Amazon SES or SendGrid. Reverse DNS is your job only for mail servers that send from IP addresses you control.