Author: Giuliano Gavazzi Date: To: Andreas Metzler, exim-users CC: Steinar H. Gunderson, 237947-forwarded Subject: Re: [Exim] Please add support for ACLs run at _start_ of data
(acl_smtp_predata)
At 5:56 pm +0100 2004/03/14, Andreas Metzler wrote: >Hello,
>I have received this as http://bugs.debian.org/237947 >On 2004-03-14 "Steinar H. Gunderson" <sgunderson@???> wrote:
>> While implementing greylisting in exim4 we came across an interesting
>> possibility: Reject not _after_ DATA, but actually on the DATA command
>> itself. (Most greylisting implementations seem to reject on RCPT, but
>> that potentially breaks callouts etc. in all sorts of ugly ways.) Ie.
>> something like:
>
>> 220 exim4 blabla
>> EHLO domain
>> 250 OK
>> MAIL FROM: <foo@bar>
>> 250 OK
>> RCPT TO: <bar@foo>
>> 250 Accepted
>> DATA
>> 401 Sorry, greylisted, try again later.
>
>> Thus, one doesn't have to waste bandwidth and processing power on
>> something that will only be thrown away later, but one doesn't break
>> callouts either.
>
>> The simplest way to achieve this would probably be adding an
>> acl_smtp_predata ACL, run at the DATA command. Would this be possible to
>> implement?
>[...]
>
>It sounds like a logical additions, I am just not sure how other MTAs
>would interact, rejecting the DATA command itself seems rather unual.
>For reference RFC2821 says about this:
I do not understand how this would be different if done at the RCPT
phase. Just send a temporary error then and you will not violate the
RFC..
