Re: [Exim] opinion on unconditional accept for postmaster

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Autor: Marc MERLIN
Data:  
Para: James P. Roberts, exim-users
CC: Mike Meredith, Giuliano Gavazzi
Assunto: Re: [Exim] opinion on unconditional accept for postmaster
On Tue, Dec 10, 2002 at 01:12:39PM -0500, James P. Roberts wrote:
> I've seen the same problem. After a over a year of operation, I have so
> far received ZERO legitimate emails to "postmaster," but quite a number


Because you're more clued that 99% of the postmasters out there, and no one
has had to contact you about a problem yet.
That may still happen one day however (I used to receive and handle all the
postmaster Email for sourceforge.net, and among other things, we had a few
rare cases of TLS problems between our exim and some other mail servers that
implemented TLS differently (Philip has since added an option to exim to
deal with that). The point being that you may always receive an Email one
day :-)

I know I eventually got so pissed off at having my mail to remote
postmasters bounce when I had problems that I implemented the postmaster
callback in exim (i.e. don't accept Email from a site as long as they don't
at least return 2xx for RCPT TO postmaster)

> of spams. I still accept all emails addressed to "postmaster" for any
> of my local domains. They all get sent to my inbox, since I am arguably
> the postmaster for all the domains I am hosting. Then I delete them by
> hand, as soon as I verify they are spam. It's not a huge problem. But
> it is annoying.


It's interesting, as while I've been postmaster for big sites, somehow, I've
never received much spam at all at those addresses (most spammers know
better than shooting themselves in the foot)

> .Is anyone out there doing something along these lines, that could share
> their technique?


I actually receive mail for postmaster and abuse, in front of any blocks I
could have. It's also very useful when I contact sites I refuse Email from
for some reason: I just change my From address to be postmaster, that way
their reply goes through even though they haven't fixed their host yet.

> Would it violate the RFC to apply RBL blocking first, before accepting
> stuff for postmaster? Seems like that would block a lot of it, but


Yep :-)
Besides, blocked people then have no recourse to contact you and tell you
the block was made in mistake (it does happen)

> might also violate the intent of the RFC. For one thing, it would
> prevent someone, who is black-listed but shouldn't be, from being able
> to contact a postmaster to let them know they are being blocked. The


Yep.

> same argument applies to pretty much any anti-spam measures, not just
> RBLs. Hmmm...


You got it :-)

> You know what? I REALLY dislike spammers. Sigh.


See, we all agree on that ;-)

One way that it a bit beyond the RFCs but that I would consider acceptable
enough for big sites is:
- refuse Email that fails SMTP callbacks, even to postmaster
The SMTP callback rejection should include the reason why the mail is
being rejected (i.e. unbounceable Email)
- accept mail to postmaster and send an autoresponder message giving your
guidelines and explaining how to contact you for each kind of problem.

Marc
--
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems & security ....
                                      .... what McDonalds is to gourmet cooking
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