[nzlug] (OT) Sorbs etc, was Exim: Limiting outgoing connections on Debian

[Simon Lyall]

On Wed, 11 Oct 2006, Robin Sheat wrote:
> On Tuesday 10 October 2006 23:30, Simon Lyall wrote:
> > a. Delayed
> > b. Being returned to the sender with an error
> > c. Being lost with no error being generated to sender or receiver.
> Aside from the first one, any remotely compliant sender shouldn't suffer from
> these. And if it does, then it was likely dropping messages randomly anyway,
> if the remote host happened to be a little flakey.

"b." is quite likely if (say) the sending mail system is only retrying
every few hours and using a different server (from a pool) each retry.

Queue handling is not something most mail servers do well and when you
have a larger system with thousands of emails in the queue then it can
take a while between each attempt.

"c." is a bit more rare but can happen, especially in cases of multiple
forwards and the like. Not to mention that with the amount of forged
emails going around bounces are pretty easy to ignore these days.

> > b. Greylisting imposes load on the mail servers of senders.
> Not much of one, provided the greylisting is implemented correctly, and it's
> only a one off generally.

You are thinking of small systems where one guy is emailing anothered.
Imagine something like trademe emailing ihug or paradise emailing Auckland
City Council. Imagine the number of emails sent per day and the size of
the sender/receiver/server listings. Remember that the sending and
receiving sites will have multiple mail servers.

Oh yeah and the helpdesks don't like it when they get customer complaints
about emailing going slow either.

"Running a large mail system ain't like dusting crops"

-- 
Simon J. Lyall  |  Very Busy  |  Web: http://www.darkmere.gen.nz/
"To stay awake all night adds a day to your life" - Stilgar | eMT.