Event Id: 623, 1022, 9791. Need to delet huge messages?

I am running exchange 2003 SP2 and I am reciving event id: 623 and 1022 and 9791 many times. Users are being locked out of exchage and I keep rebooting the server for messages from the local delivery queue to start being delivered again for a short period of time then the the cycle of errors start, users are locked out again then I restart.
 At the same time I keep getting many event id: 103 " F-secure scanning of xxxxx  was aborted due to exceeded scanning limit. The file may be in use or reading it was too slow (e.g network connection was under stress).
From the seach I have done !!  it looks like I have large e-mails messages in the mailbox.
If you agree then "How can I delet  large messages from the mailboxes from exchange".
For example delet " All messages greater that 50mb" .

If you diagree then what could be the solution to my problem?
Thanks for your support inadvance.
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jkodiAuthor Commented:
This problem start yesterday ... Help.
Glen KnightCommented:
This is caused by a 3rd party product that is interfering with the SMTP feed.

What 3rd party Virus/SPAM software do you have installed? Remove it and reboot the server, does the problem stop?

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jkodiAuthor Commented:
Yes..Removed all third party softwares then it worked.
Glen KnightCommented:
So if what I suggested resolved the problem for you why is it only worth a B grade?
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