[Mimedefang] Requiring FQDN in HELO

James Ebright jebright at esisnet.com
Wed Dec 28 16:00:17 EST 2005

In addition, I believe rejecting email due to an invalid HELO/EHLO is a 
rfc violation in of itself (MUST NOT even). That said, the only ones I 
reject are the ratware ones that say they are me (my ip blocks or 
localhost or my own FQDN).  ;-)


Cormack, Ken wrote:

>>   The ultimate goal to allow filter_sender to reject any E-Mail where
>>the HELO is a blank string (spaces) or something like "localhost"
>>without any qualification. Are there any reasons that legit,
>>reasonbly-standards-compliant senders would do those things?
>In my environment, I've noticed that WAY too much valid email is sent from
>hosts that are lame in this respect, sending partial or non-FQDN hostnames,
>or that identify themselves with a hostname/domain/"tld" that might be
>appropriate for the sender's INTERNAL/PRIVATE environment
>(myhost.nowhere.not).  To evaluate YOUR potential for success/risk, you
>might try just adding something in filter_sender, to perform logging-only,
>of the value of $helo.  Then, you can review your list of log entries.

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