Skip to content


Subversion checkout URL

You can clone with
Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

60 lines (35 sloc) 1.699 kB


This plugin performs a number of checks on the HELO string.

HELO strings are very often forged or dubious in spam and so this can be a highly effective and false-positive free anti-spam measure.


  • helo.checks.regexps

    List of regular expressions to match against the HELO string. The regular expressions are automatically wrapped in ^ and $ so they always match the entire string.

  • helo.checks.ini

    INI file which controls enabling of certain checks:

    • check_no_dot=1

      Checks that the HELO has at least one '.' in it.

    • check_raw_ip=1

      Checks for HELO where the IP is not surrounded by square brackets. This is an RFC violation so should always be enabled.

    • check_dynamic=1

      Checks to see if all or part the connecting IP address appears within the HELO argument to indicate that the client has a dynamic IP address.

    • check_literal_mismatch=1

      Checks to see if the IP literal used matches the connecting IP address.

    • require_valid_tld=1

      Requires the HELO argument ends in a valid TLD if it is not an IP literal.

    • skip_private_ip=1

      Bypasses check_no_dot, check_raw_ip, check_dynamic and require_valid_tld for clients within RFC1918, Loopback or APIPA IP address ranges.

    • [bigco]

      A list of =[,...] to match against. If the HELO matches what's on the left hand side, the reverse-DNS must match one of the entries on the right hand side or the mail is blocked.

Jump to Line
Something went wrong with that request. Please try again.