How to know if I'm blacklisted

Matt Kettler mkettler at
Thu Jan 17 22:46:23 GMT 2008

Glenn Steen wrote:
> On 16/01/2008, Matt Kettler <mkettler at> wrote:
> (snip)
>> The other part is your HELO is mail2.CANAL4. That really should be a valid
>> hostname. It's technically not against the RFC's to spew garbage here, but it
>> does show poor server administration, and some misguided sites seem to think
>> HELO must be a valid hostname and filter such things (the RFC's merely say
>> SHOULD, not MUST). You might want to fix the hostname your mailserver thinks of
>> itself as.
> Um, not misguided as in "that could be anything". At least 2821 is
> pretty clear that the argument to EHLO (use of which is only a SHOULD
> in conjunction with the stipulation that "if you don't use EHLO you
> MUST use HELO", more or less) need be a FQDN, unless you are operating
> in a situation where such isn't valid (no valid reverse lookup or
> dynamic allocation of IP etc), in which case it "should" be an address
> literal... So rejecting on an invalid domain (or address literal)
> SHOULD be quite OK;-).

True, but if a system is using HELO instead of EHLO, anything goes. There's no 
MUST in the requirements for HELO, merely SHOULD.

ie: it is 100% in RFC spec to issue:

HELO somerandomgarbage

Although it is not in-spec to do that for EHLO, as you point out.

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