---
name: "Mail::SpamAssassin::Util::RegistrarBoundaries"
section: "3pm"
platform: "linux"
package: "spamassassin"
version: "3.4.0-6"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/Mail::SpamAssassin::Util::RegistrarBoundaries"
---

# Mail::SpamAssassin::Util::RegistrarBoundaries(3pm)

domain delegation rules

## NAME

Mail::SpamAssassin::Util::RegistrarBoundaries - domain delegation rules

## METHODS

- ($hostname, $domain) = split\_domain ($fqdn)

  Cut a fully-qualified hostname into the hostname part and the domain part, splitting at the DNS registry boundary.

  Examples:

  ```
      "www.foo.com" => ( "www", "foo.com" )
      "www.foo.co.uk" => ( "www", "foo.co.uk" )
  ```

- $domain = trim\_domain($fqdn)

  Cut a fully-qualified hostname into the hostname part and the domain part, returning just the domain.

  Examples:

  ```
      "www.foo.com" => "foo.com"
      "www.foo.co.uk" => "foo.co.uk"
  ```

- $ok = is\_domain\_valid($dom)

  Return `1` if the domain is valid, `"undef"` otherwise.  A valid domain (a) does not contain whitespace, (b) contains at least one dot, and (c) uses a valid TLD or ccTLD.