Re: [exim] Is there and logical reason to reject mail from: …

--On Saturday, October 16, 2004 5:41 pm -0400 "Greg A. Woods"
<woods@???> wrote:

> [ On Thursday, October 14, 2004 at 17:24:44 (-0700), Tor Slettnes wrote: ]
>> Subject: Re: [exim] Is there and logical reason to reject mail from: <> ?
>>
>> You keep missing the point. It is not about the original spam; the
>> issue is the "backscatter" (a.k.a. collateral spam) generated by
>> post-SMTP spam/virus filters elsewhere. These send a DSN to the
>> original sender addresss (in some cases, that could be
>> "postmaster@???").
>
> It doesn't really matter if it's backscatter or not.
>
> There is still no _valid_ excuse for rejecting mail transactions
> addressed to the/any postmaster mailbox _just_ because they use a null
> return path.
>

Nobody is talking about ONE reason. THREE conditions have to be matched,
afaict:

1. The email is addressed to POSTMASTER (a commonly forged email address).
2. POSTMASTER is an address that doesn't send mail.
3. The email has a null sender address - and is, therefore, an automatic
reply.

A little bit of logic tells us that the email must therefore be
backscatter, a callout, or a manual test of whether I accept email to
postmaster from the null sender.

The RFCs tell me to accept email addressed to postmaster such that people
can easily contact me. Provided I don't do callouts on email addressed to
postmaster, rejecting backscatter shouldn't hurt there.

BTW, I don't actually reject bounces addressed to postmaster, but I think I
will begin doing so soon enough.
--
Ian Eiloart
Servers Team
Sussex University ITS