> ## Knowledge Base Index
> Fetch the complete knowledge base index at: https://krystal-dev.crisp.help/sitemap.xml
> Use this file to discover available pages before exploring further.
> Pure-Markdown content can be obtained by appending a '.md' suffix to the content URLs listed in the sitemap (without the trailing slash).

# Setting up Reverse DNS (RDNS) PTR records for VPS or Dedicated servers

DNS provides a way to map a server name to an IP address e.g. www.krystal.uk = 77.72.0.35

It also provides, via Reverse DNS (RDNS), a way to do the reverse check, from an IP address to a server name via PTR records.

This can be particularly important if you are running an email server. Remote mail servers will often perform an RDNS lookup to ensure that the IP address the request came from matches the domain name of the incoming email. If you don't have RDNS setup your email may not be accepted.

RDNS PTR records can be requested by contacting Krystal Support.

Please provide details of the VPS/Dedicated server IP address and the fully qualified domain name of the server (FQDN) e.g. if you've named your VPS `server` and your domain is `example.co.uk` then your FQDN would be `server.example.co.uk`

* * *

* * *