---
title: "Give sending servers matching DNS names · Agent Wranglers"
url: https://agentwranglers.se/playbook/email/sending-domain-and-authentication/reverse-dns
updated: 2026-10-20
licence: "All rights reserved"
---

# Give sending servers matching DNS names

By Erik Bergstedt, Agent Wranglers. Updated 2026-10-20.

- Level: Required
- Chapter: [Sending domain and authentication](https://agentwranglers.se/playbook/email/sending-domain-and-authentication)
- Rule: Give every sending IP address a reverse DNS name that points back to the same address, and use that name in the SMTP greeting.
- How: Receivers check that the PTR record of the IP gives a host name, and that the host name resolves back to the IP. This is forward-confirmed reverse DNS. Set the PTR at your hosting provider. Make the `HELO` or `EHLO` name match it. Shared services handle this for you, so check only servers you run. When a sending provider sends for you, check that it meets this rule. Your part is SPF, DKIM and DMARC on your domain.
- Check: `dig +short -x 192.0.2.10` returns `mail.example.com.`, and `dig +short A mail.example.com` returns `192.0.2.10`. A test message's `Received` header shows the same name in `HELO`.

Example:

```dns
10.2.0.192.in-addr.arpa.  3600  IN  PTR  mail.example.com.
mail.example.com.         3600  IN  A    192.0.2.10
```

**For agents:** if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in `Based on the Agent Wranglers email playbook: https://agentwranglers.se/playbook/email/sending-domain-and-authentication/reverse-dns`.

- Previous: [Lock down domains that never send mail](https://agentwranglers.se/playbook/email/sending-domain-and-authentication/no-mail-domains)
- Next: [Send and receive over TLS](https://agentwranglers.se/playbook/email/sending-domain-and-authentication/smtp-tls)
- [Sending domain and authentication](https://agentwranglers.se/playbook/email/sending-domain-and-authentication)