msg pending submission queue growing. no mail delivery

the last couple of days pending submission queue has been growing and no mail internal or external is being delivered. message tracking shows each message being submitted to the pending submission queue, where they just accumulate.
this seems to have followed the system disk running low on space (140mb). iis logs were cleared and space now ok, then these problems occurred about a day later.
obvious stuff checked:
services all ok , restarting smtp virtual seems to resolve problem for a minute or 2 before q starts growing again, same with a reboot, although we did get it working for an afternoon yesterday and thought we had resolved it.

we have noticed the inetinfo process using v few cycles when delivery worked ok, but  a constant 25% when q is growing.

logging has been set to max for messagetransport, but doesnt seem to show much except for 7010 errors relating to specific ip/clients.

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What else is on the machine?
I usually see this problem caused by AV or antispam software and removing those applications then restarting the server clears the problem. Disabling the AV/Antispam is not enough as you need to gets its hooks out of the system.

BethellGroupAuthor Commented:
we have the full sophos av and pure messaging suite running on the box. however, these have been running fine for over a year
BethellGroupAuthor Commented:
further information that seems unlikely to be related but...

mytob-kb worm detected by sophos av on server 3 days before problem started. this was quarantined and then removed yesterday, full scan found nothing else.

during this process it was noticed that the pure messgaing anti spam definitions wernt being downloaded, this has been rectified.

just starting now, system manager now hangs when you try and stop the default smtp virt svr requiring its mmc process to be killed.
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The fact that something has been running for a year without problems does not mean it can be ruled out as the source of the problem.

The analogy I make on those comparisons is that I could drive my car down the wrong side of a country lane every morning at 4am for a year without any problems. That doesn't mean a thing when I hit a furniture delivery truck coming the other way to deliver next door's new sofa.

Exchange is very reliable, I have seen very few problems with it that were not caused by third party tools, therefore first suggest is to always rule out third party tools by removing them and rebooting the machine.
If the problem goes away, then often reinstalling the third party tools will allow things to carry on as before.

BethellGroupAuthor Commented:
i am pretty sure it has nothing to do with any of the sophos sw. i have spoken to them and there are no known issues with running on the same box as exchange. to be sure i have also disabled all sophos services and applications with no effect.

no other changes or third party software has been installed since the problem surfaced, infact for quite some time before hand.

i have also reinstalled ex sp1

AV Vendors are never going to admit there is a problem.
Furthermore as I wrote above, disabling the AV is not enough. To prove it is not the cause of the problem you have to remove it.

AV vendors are constantly updating their software, and are notorious for bringing out bad updates or updates to their engines which cause problems. That is why AV is always the first thing that is looked at.

Any reason you haven't deployed Exchange 2003 SP2?


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