How to know if I'm blacklisted

Matt Kettler mkettler at
Thu Jan 17 22:48:45 GMT 2008

Glenn Steen wrote:
> On 17/01/2008, Glenn Steen <glenn.steen at> 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;-).
>> In reality, there might be a few admins that get this wrong. Bah,
>> couldn't care less, this drops a huge amount of spam for me.
>> Cheers
> Further... As you know, RFC821 isn't too specific about the argument
> to HELO (which is all there is for older specs), but this is ...
> rectified in RFC1123 (along with a few other protocols that weren't
> that well defined from the start:-). Below is a quote of the section
> about the HELO command, where it clearly states a MUST (which isn't
> that clearly stated in the definition of EHLO in RFC2821, I'll grant
> that:-). And in the DISCUSSION you see that the standard even suggest
> rejection on *pure bad formatting* as a very viable option, with a
> well-defined return. 2821 obsoletes (among others) and updates 1123,
> so ... this is clearly a MUST and not SHOULD.
> Go ahead and start using this Matt, it is very effective;-).

One thing, by your own citation, you MUST NOT use the verification of the HELO 
to refuse a message.

So, using such validation to refuse mail is RFC non-compliant.

> ------------
>	   However, the
>          receiver MUST NOT refuse to accept a message, even if the
>          sender's HELO command fails verification.

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