Re: [Exim] Server response to error codes

On 6/28/2004 5:38, "Craig Jackson" <cjackson@???> wrote:

> On Mon, 28 Jun 2004 00:12:23 -0400 (EDT)
> "Greg A. Woods" <woods@???> wrote:
>
>> [ On Saturday, June 26, 2004 at 16:29:25 (-0500), Craig Jackson wrote: ]
>>> Subject: [Exim] Server response to error codes
>>>
>>> Does anyone have a source of information on various mail servers and
>>> their response to error codes?
>>>
>>> Recently I implemented greylisting on my server named Mailscan (Exim
>>> 4.34); but I noticed that our Groupwise 5.5 bounces the outgoing mail to
>>> the greylisting Exim server at 451 after RCPT. This is a test situation
>>> now.
>>
>> "bounce" and "451" does not compute. :-)
>>
>> As we all know any 4xx response code is a _temporary_ error.
>>
>> Do you mean the GroupWise server returned a 451 response to the RCPT
>> command sent by Exim? Or do you mean the GroupWise server treated a 451
>> response to its own RCPT command as a permanent error and did not retry
>> delivery of the message as it should?
>>
>> I'm guessing you mean the latter, given the context.
>>
>> Have you checked to see if there are any configuration options on the
>> GroupWise server that might change its behaviour?
>>
>>> I need to know what other mail servers are going to do with a 451.
>>>
>>> Any information sources on this?
>>
>> I've never run across any such list that even begins to cover just the
>> most common servers.
>>
>> A counter question might be: Do you have any idea what types of mail
>> servers make up the majority of those originating the normal legitimate
>> traffic your site receives?
>>
>> I.e. since you don't care what any sources of unwanted traffic do with
>> any temporary error code you might send them (that's the whole point of
>> implementing something like greylisting after all, isn't it?) so if you
>> narrow your question down to just those specific types of mailers that
>> you know you get the majority of your legitimate traffic from then you
>> can begin to target your question to those who are more likely to be
>> able to answer it. :-)
>>
>> --
>
> Greg,
>
> I've never bothered with the Groupwise server, never had cause to. But looks
> like it's time to do some fixin', so right, the latter is correct.
>
> I realize it was sort of a hair-brained question, but we get mail from
> probably every type of server known, but mostly exchange. Yours is a good
> suggestion, though. I'll compile a list of sending servers, esp the important
> mail. My fear in implememnting something like greylisting is that if I get a
> bounce the FIRST time I test it from another server, then it is 100%
> guaranteed that one of the top people in the firm will have a similar problem
> several times within the first 2 months and will probably be pissed -- at me.
> We'll see. Because on my test server, ZERO spam is getting through so far, and
> only one false bounce positive.
>

There are several servers which need whitelisting. Our first example was
the Yahoo Groups servers, which treat a 451 in response to RCPT TO: as
meaning "OK, this message and future messages in this group for this member
go into the Web interface instead of mail".

There are others you may as well whitelist...the outbound servers which send
you lots of mail and behave properly, for example. They might as well not
suffer the first-time delay.

We had one the other day which misbehaved...we whitelisted it and sent a
report off the the developer, who claims to have added a fix to the schedule
for the next version.

I've forgotten whether the current version of Groupwise misbehaves or
not...certainly some older ones do.

Given the RFCs, I believe Exim has no choice but to say 503 in response to
DATA if there were no valid recipients, pipelining or not. Which is really
very odd in that RCPT TO: and DATA are in the same command group for
pipelining purposes. We send lots fewer 503s now that we have turned off
pipelining globally.