Some emails getting stuck in the Exchange Queues

We have 3 seperate incidents at different locations where some emails are being stuck in the Exchange queue and marked as scheduled but never goes Active to send (running SBS2003 R2). This all started happening when an Automatic Update started to run last week (21 JAN 08)  and after this, some emails were stuck in the queue and some were not.

There are no errors in Event Log, all services running fine and some external emails are going through. Only change was last week's Automatic Update.

Our temporary work around is to run MTA stack services which seems to allow all emails to go through (but it makes no sense) however, now emails stays in the queue until we force connection. Any ideas?
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The email that stuck in the queue are from postmaster or they have genuine user address on it... also, if possible check if the email getting stuck in queue are for specific domain or any in general
techcorpAuthor Commented:
These are legitimate email addresses, these are not spam emails.
The queues are not from post master, we've monitored some individual emails and they come up in the queue as scheduled. When Force Connection, they send out successfully.
techcorpAuthor Commented:
When to SMTP connector properties (this connector is set by default from SBS). In Delivery Options then Specify when messages are sent through this connector
techcorpAuthor Commented:
continue from previous entry...

In Delivery Options then Specify when messages are sent through this connector  to "Always Run"

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