How to know if I'm blacklisted

Matt Kettler mkettler at
Fri Jan 18 18:18:47 GMT 2008

Glenn Steen wrote:

>> So, using such validation to refuse mail is RFC non-compliant.
> The magic is in:
> -----
>              Note also that the HELO argument is still required to have
>              valid <domain> syntax, since it will appear in a Received:
>              line; otherwise, a 501 error is to be sent.
> -----

Fair enough, so you can deny it if it doesn't conform to the domain syntax.

Note this doesn't mean it must be resolvable, or even be a valid domain, it just 
has to logically conform to the syntax requirements of a domain. "mail2.canal4" 
is valid domain syntax, even if it's not a valid domain.

> ... which is a bit further down. Your quote below is in regard to
> doing an MX lookup on the string.

Or any DNS lookup. It would appear the only time you can refuse is if it's 
syntactically invalid.

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

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