maillscanner/postfix saturates bandwidth :-(

Dave Helton dave at KD0YU.COM
Mon Sep 24 19:47:55 IST 2012

> > I'm trying to figure out the best way to deal witih this moving
> > forward, is there additional throttling I need to do at the postifx
> > level or the mailscanner level or something else.  I was also
> > surprised as my understand of postfix is that it does connection throttling
> by default.
> Just a thought if you have spam tests enabled this will be doing a lot of dns
> lookups on every email - this could be the cause of some of the bandwidth -
> installing a caching nameserver on the server will stop a lot of this happening
> - especially if its the same email going to 100 recipients (urghh!!!) emails imo
> should be individually addressed, using bcc/cc is not the way to send a
> mailshot - its got a very high chance of landing in spam/junk folders for not
> being personally addressed.

I would agree with Ian here, plus a couple other points.
Your router is probably your dns server for internal to external resolving, and since
it doesn't have a lot of memory, it has to look up each domain on the fly.  Not
terribly bandwidth intensive for dsl, but it's still a lot of overhead... and slow.
A caching dns server for the mail server would help a lot.

Second, you are probably subject to one of our best anti-spam mechanisms...
greylisting.  That is, unless everyone on your mailing list has you on whitelist.... umm
doubtful.  Again, bandwidth intensive.

Last, there are a lot of great mailing list programs out there that run specifically on an
Apache server.  Even MailMan would work.  Both you and your customer could access
the interface and you could do remote support for them, a nice selling point.
This could also turn out to be one of those "the best laid plans" ordeal.  So give it some

My point is, take everything out of the hands of that Exchange server and put it in a
controlled environment, meaning throttling, reporting, and easily accessible to you.
I would also try and convince your customer that a LookOut distribution list is not an
adequate substitute for the real thing since they have 'evolved' beyond it  ;-)

--Dave, KD0YU

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