[Mimedefang] $helo versus $ip

[kamal]

"RFC 1123, Requirements for Internet Hosts -- Application and Support" 
says the following on this issue.

The HELO receiver MAY verify that the HELO parameter really
corresponds to the IP address of the sender.  However, the
receiver MUST NOT refuse to accept a message, even if the
sender's HELO command fails verification.

....

IMPLEMENTATION:
When HELO parameter validation fails, a suggested
procedure is to insert a note about the unknown
authenticity of the sender into the message header (e.g.,
in the "Received:"  line).