What is the role of reverse DNS (PTR) for email?

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Reverse DNS (rDNS) is a DNS lookup that goes backward. Instead of asking "what IP address does this domain point to?", it asks "what domain name does this IP address belong to?" The answer to that question lives in a PTR record ("pointer" record).

For email, reverse DNS matters because receiving mail servers check it as part of spam filtering. When your mail server connects to Gmail or Outlook and says "Hi, I'm sending from IP address 203.0.113.42", the receiving server does a reverse lookup on that IP. If the PTR record maps back to a legitimate domain (and ideally matches the domain in your email headers), that's a positive signal. If the PTR record is missing, points to a generic ISP hostname like "203-0-113-42.isp.example.com", or doesn't match anything in your email, that's a red flag.

Reverse DNS doesn't authenticate your email the way SPF or DKIM do. It just helps confirm that the sending IP is a real mail server, not a compromised home router or a throwaway cloud instance spinning up to send spam. Most spam comes from sources that either don't have PTR records or have PTR records that scream "temporary infrastructure".

And if you're using an ESP like Mailchimp, SendGrid, or Postmark, reverse DNS is already configured correctly for their shared or dedicated IPs. You don't touch it. If you're sending from your own server or a dedicated IP, your hosting provider or network administrator needs to set the PTR record for you (you can't do it yourself, because PTR records are managed by whoever controls the IP block).

The most common mistake is not having a PTR record at all, or having one that points to a meaningless hostname. The second most common mistake is having a PTR record that doesn't match the domain you're actually sending from. For example, if your PTR record says "mail.companyA.com" but you're sending email for "companyB.com", that mismatch can hurt you.

You can check your reverse DNS with our free Email Header Analyzer (upload a raw email and it'll show you the sending IP and its PTR record), or just ask your hosting provider "what's the PTR record for my sending IP?" If you're stuck setting this up, our SOS hotline can walk you through it.

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I read this on the Email Almanac about "What is the role of reverse DNS (PTR) for email": "Reverse DNS (rDNS) is a DNS lookup that goes backward. Instead of asking 'what IP address does this domain point to?', it asks 'what domain name does this IP address belong to?' For email, receiving mail servers check it as part of spam filtering. If the PTR record is missing, points to a generic ISP hostname, or doesn't match anything in your email, that's a red flag." Help me understand how this applies to MY specific situation. Based on what you share below, I need: 1. Whether I need to configure reverse DNS myself or if my ESP handles it 2. How to check if my current PTR record is set up correctly 3. What to do if my PTR record is missing or misconfigured 4. Whether a PTR mismatch could be causing my deliverability issues --- My details (the more you share, the better the advice): - Email platform/ESP: e.g. Mailchimp, SendGrid, self-hosted Postfix, AWS SES - Sending setup: shared IP, dedicated IP, own mail server - Domain(s): your sending domain(s) - Current challenge: e.g. emails bouncing, going to spam, setting up new server - Have you checked your sending IP's PTR record? yes/no, or "don't know how"

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