[Greylist-users] An approach for reducing mail loss with greylisting
ronaldoussoren at mac.com
Mon Nov 13 09:43:16 PST 2006
On 13 Nov 2006, at 2:10 PM, William Blunn wrote:
> Ronald Oussoren wrote:
>> All MTAs should be able to deal with this, you can already get 4xx
>> status codes due to full mailboxes and other transient failures.
> Sorry, no.
> All (legitimate) MTAs should be able to deal with transient
> failure, period.
> The fact is that they don't.
> Moving your transient failure indication after the end of DATA
> isn't a panacea for broken MTAs.
> Not only that but I don't even think that moving there would give any
> overall benefit versus tempfailing before DATA.
> Indeed I have heard tell that some (broken) MTAs ignore errors
> after the
> end of DATA.
There are definitely MTAs that don't handle 4xx errors at the
traditional place to do greylisting. I've seen both servers that
bounce immediately (e.g. treat the 4xx as a 5xx error) and servers
that completely drop mail. That was a major reason for dropping
greylisting, although I'm interested in trying again now that
greylisting has matured because greylisting was very effective at
dropping unwanted mail.
My gut feeling is that MTAs will be better at coping with 4xx errors
at the end of the DATA command because that's where you traditionally
get those when mailboxes are full.
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