[Mimedefang] Requiring FQDN in HELO
Dirk the Daring
dirk at psicorps.org
Wed Dec 28 13:01:05 EST 2005
I've noticed a lot of SPAM does not have an FQDN in the HELO. It'll
have just "localhost" or even omit a hostname entirely. Obviously, if
the HELO is an IP address in square brackets, that's fine.
Is there any danger of rejecting "legitimate" E-Mail if I write my
1) Absent an IP address in square brackets, require a
an alphanumeric string in the HELO
2) Reject a HELO where the alphanumeric string is not
a FQDN (using a regex looking for at least
one "." in the HELO string)
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?
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