Hi there,
Managing our campus' central mail server, I've been running Exim for a
number of months now, and I'm very happy with it. Although the load is a
lot lower than the records quoted here (around 17k per day), it still
serves around 30 NetWare file servers.
Which brings me to the problem. These servers typically time out when
receiving large (>5MB) messages, causing these to get stuck in the mail
queue. I though it would be save to use Exim's wonderful
message_size_limit = 5000K
but I was wrong: our current usage-based Internet billing structure
meant that limiting the message size heavily loaded our incoming line,
as some useless MTAs keep on re-transmitting after having their messages
rejected when they're too large. According to spec.txt par. 43.4:
>Some MTAs continue to try to deliver a message even after receiving a >5xx
>error code for MAIL FROM. The alternative configuration option
>sender_reject_recipients is provided for use in such cases. It accepts >the
which works fine, but isn't exactly automated, as I have to add those
hosts manually until the problem goes away. The fundamental problem is
that Exim first has to accept that 5MB of data before rejecting it, at
which point the University has already paid for that traffic !
I suppose this is a fairly general problem when one wants to limit
message sizes: does any one have suggestions of how I can better handle
this situation ? (oops, apart from the obvious negotiation of non-usage
based cost stuctures; that's already underway-although that's not the
only consideration: obviously we want to conserve bandwidth in any way
so that it may be used for more sensible purposes)
--Charl
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Charl J. Barnard | NW II Building Room 5-1.3
charl@??? | +27-12-420-2444 (Office)
Linux for life
