We are being told that this is a known "limitation" of iMail; it can't handle more that 55 or so simultaneous SMTP connections.
the problem is not only from legit connections but from spam that can typically consumes more than 50% of the SMTP connections, based on spam being well over 70% of all mail volume on many sites. Rejecting msgs to unknown recipients is also a big consumer of SMTP connections.
Seems hard to believe that iMail is advertised as "unlimited" and can't handle more than 55 connections.
55 is sufficient for a large volume of legit msgs, but the 55 is not available for legit traffic.
But all of my testing has been consistent with this; connection is real slow when the number gets over 45 or so.
other symptoms seen by the sending MTA are IMail give "connection refused" and "timeout after <SMTP command>"
Anyway, we are looking for a product to set up that clients can use as their SMTP Server instead of the current POP3 iMail server.
By using a separate box as defensive MX, you will reduce dramatically the number of IMail SMTP connections wasted on spam, allowing more sessions for legit SMTP AUTH sessions.
At least as a workaround until iMail fixes this or we split the load to 2 iMail servers,
... each of which will still have 50+% of its SMTP bandwidth wasted by spam. Not progress
or replace iMail if we have to.
Keep Imail and its hardware, probably good for several more years. Try the above approach, with IMGate in my sig.
Len
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