Domains and DNS

What is a PTR record?

An A record answers "what address does this name have?" A PTR record answers the exact opposite question, and most mail servers refuse to talk to you if you cannot answer it.

A PTR (Pointer) record maps an IP address back to a host name - the reverse of what an A record does. Given the IP address 203.0.113.7, a PTR lookup returns something like mail.example.com, and a receiving mail server checks that this reverse lookup exists and roughly matches the sending server’s own identity before it will accept a message. Unlike ordinary DNS records, a PTR record for a given IP address can normally only be set by whoever controls that IP block - which in practice means your hosting provider or ISP, not your domain registrar.

Worked out 2026-09-18 (IST) · standard reverse DNS delegation under the in-addr.arpa (IPv4) and ip6.arpa (IPv6) zones

Forward vs reverse, side by side

The two directions of DNS
	A record (forward)	PTR record (reverse)
Question answered	"What address does this name have?"	"What name does this address belong to?"
Looked up from	The domain’s own DNS zone	The in-addr.arpa zone, delegated by whoever owns the IP block
Who can set it	Whoever controls the domain’s DNS	Whoever controls the IP address - usually the hosting provider or ISP
Most common consumer	Browsers, apps, anything resolving a name	Receiving mail servers, and some spam and fraud filters

Why this specifically breaks self-hosted email

A mail server on shared hosting or a managed provider (Google Workspace, Microsoft 365, Zoho) inherits a correctly configured PTR record automatically, because the provider controls the whole IP block and sets it up for every customer. A mail server run on a general-purpose cloud instance - a VPS spun up to send transactional email, for example - often has no PTR configured at all by default, which is why "why do my emails go to spam" so often turns out to have nothing to do with the message content and everything to do with a step that was never done. See why emails go to spam for the full checklist, of which PTR is one item alongside SPF, DKIM and DMARC.

How to check whether yours is set correctly

Three checks
Check	How	What a pass looks like
Does a PTR exist at all?	Reverse-lookup your sending IP	Returns a real host name, not "no PTR record found"
Does it forward-confirm?	Look up the A record for the returned host name	That A record resolves back to the same IP you started with
Does it match your HELO name?	Compare the PTR result to what your mail server announces in its SMTP HELO/EHLO	Same host name, or at least the same domain

Sources: IETF RFC 7208 (SPF), RFC 6376 (DKIM), RFC 7489 (DMARC), Google Workspace Email sender guidelines (effective 1 February 2024) and Microsoft’s Outlook.com sender requirements (effective 5 May 2025).

Check your own numbers

Check whether an IP address has a matching PTR record, and what it resolves to.

DNS LookupA, AAAA, MX, NS, TXT, CNAME and SOA records, live from the resolver.

Frequently asked

Why do mail servers care about PTR records specifically?

Because a forward-confirmed reverse DNS match - the PTR points to a host name, and that host name’s own A record points back to the same IP - is one of the cheapest signals of legitimacy a receiving server can check. A server sending mail with no PTR record at all, or a PTR that points somewhere unrelated (a generic ISP hostname, for instance), looks exactly like the pattern a spam operation would produce, and is often rejected or heavily penalised on that basis alone.

How do I set a PTR record for my server?

Through whoever controls the IP address, not your DNS provider. On a cloud server that usually means a "reverse DNS" or "PTR" field in the cloud provider’s network console; on a dedicated server or colocated IP block, it usually means a support request to the ISP or data centre that allocated the address.

Does a PTR record need to exactly match the domain in my email address?

No, but it should be a real, resolvable host name, and it should ideally match the host name your mail server announces during the SMTP handshake (the "HELO" name). A mismatch between HELO and PTR is a lesser flag than having no PTR at all, but a generic provider-assigned PTR like host-203-0-113-7.isp.example.net is still weaker than a proper mail.yourdomain.com.

Is a PTR record the same thing as an MX record?

No - they point in opposite directions and answer different questions. An <a href="/answers/what-is-an-mx-record/">MX record</a> says which server should receive mail FOR a domain. A PTR record says what host name an IP address belongs TO. A working mail setup needs both, plus SPF and DMARC on the sending side.

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