How to know if I'm blacklisted

Matt Kettler mkettler at
Thu Jan 17 23:24:54 GMT 2008

Matt Kettler wrote:
> 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.

Note: I retract this based on RFC 1123, however, RFC 1123 does prohibit refusing 
mail based on HELO verifications.

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