[Greylist-users] Why is there a punctuation "rule" ?

[John W. Baxter]

On 2/22/06 8:45 AM, "Dennis Wynne" <DWYNNE at equinoxis.com> wrote:

> I noticed in the log I am giving out 501 errors with:
> 
> "Malformed envelope from address: Invalid punctuation characters"
> 
> This appears to be legit mail for my users from things like a Microsoft
> mailing list:
> 
> <10_302356_odpHB3m/yc2HOh5z4CepQC at newsletters.microsoft.com>
> 
> In this case the forward slash seems to be the problem, I have others with
> an = sign in it.
> 
> 1) What is the reason behind this "rule" in relaydelay.pl ?
> 2) How can I accept this mail (assume I can't get the sender to remove the
> punctuation characters) ?
>    a) If I whitelist the sending IP will it bypass this check?
>    b) Can I comment out this check or remove the = and / from it?

The RFCs indeed allow many strange characters  (almost anything that is
properly escaped or quoted).  Sites that *use* such characters are going to
have trouble in the actual (as opposed to the RFC) Internet, as many other
sites will be unhappy with them.

I'm not convinced, however, that it is greylisting's job to do this
filtering; it seems to me that it should be up to the underlying MTA.  (The
default Exim configuration disallows @ % ! / | and also leading "." .  Oops,
those are the rules applied to mail to "local" domains, a similar but
gentler rule applies to outgoing mail.)  The discussion of that in the Exim
specification is too long to copy here.

What greylisting does need to do, at a minimum, is protect itself from
characters which will upset its underlying database, either by banning the
characters or by properly quoting them where they appear in data heading
toward the database.

We don't use relaydelay.pl for our greylisting, so I haven't looked at it.

  --John