There is a problem that its hard to come up with metrics for best large recipient list delivery that work across a range of MTAs.
My own feeling (experience based feeling, but I haven't specifically sat down and benchmarked/analysed its behaviour) for exim is that I would tend to have a maximum number of recipients for a single SMTP transaction of ~500 recipients. I would tend to keep simultaneous injects down to around 4 at a time... although this has even less basis that the 500 recipients limit. Exim will take advantage of multiple recipients on the same MX, but you can basically assume it will not take advantage of multiple queued messages going to the same MX (except under particular circumstances). Hence I would in general do the sort/clump by reversed domain name thing since that should win in many cases.
bwarsaw@python.org said:
So with the next check-in, the chunking algorithm is to create 4 buckets: .com, .net/.org, .edu/.us/.ca, everything-else. Chunks in these buckets are no bigger than SMTP_MAX_RCPTS and buckets are not back-filled.
Thats a very parochial view of the world (he says tongue firmly in cheek). Us UK based people would probably find a different balance would work better for us :-)
Nigel.-- [ - Opinions expressed are personal and may not be shared by VData - ] [ Nigel Metheringham Nigel.Metheringham@VData.co.uk ] [ Phone: +44 1423 850000 Fax +44 1423 858866 ]