Re: smtp time spam filtering

[Paul Johnson <baloo@ursine.ca>]

David Hart wrote:

> On Mon 2007-02-26 14:26:58 -0800 Paul Johnson wrote:
>> David Hart wrote:
>> > On Sat 2007-02-24 21:03:11 -0500 Greg Folkert wrote:
>> >> 
>> >> Bouncing... bingo. If the sender doesn't handle it properly, it isn't
>> >> my problem.
>> > 
>> > You've already outlined a case where bouncing spam became your problem.
>> > You said in an earlier mail "I used to not whitelist murphy, but that
>> > got me auto-unsub'd from (most) Debian lists I subscribe to, for
>> > "bouncing" the SPAM"
>> 
>> 4xx rejects work better than 5xx for content-related rejects:  After all
>> there is a chance the message would be accepted under better
>> circumstances
>> in such a case.  Or read the list via
>> nntp://news.gmane.org/gmane.linux.debian.user instead.  :o)
> 
> Why would a message identified as spam be identified as anything else at
> a later date and why would those be "better circumstances"?

They wouldn't because the content is the same.  5xx means that you won't
ever accept mail for that box for whatever reason, 4xx is more indicative
of a transient problem such as a mailbox being full or caught by a content
filter.

> How does 4XXing the message to the mailing list help?  Surely you
> are giving the list server a bit extra work to do as it will keep
> retrying the message until it times out after a few days?

4XX responses don't get you unsubscribed automatically without notice like
5XX responses will.  After using the list directly for years, I've found
it's less bother to use the newsgroup on gmane instead.