Slow delivery from Exchange 2003 to 2010

I have Exchange 2003 and Exchange 2010 running in co-existance.

Everything works inlcuding bi-directional email flow between the two and OWA.

The difficulty now is that email flow from Exchange 2003 and 2010 is slow.  Users are reporting delays of 10-20 minutes.  Emails from Exchange 2010 to 2003 is immediate.

Checked the Exchange 2003 Routing Group Connector queue and it routinely has messages whereas the other queues are empty.
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mcnuttlawAuthor Commented:
Turns out it was a firewall routing rule.
What are teh costs set on those routing groups ? if it is high, might need to reduce that.

else have you tried re-creating it ?
Run BPA from the 2010 server and run health check on both any critical issues.
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Rajith EnchiparambilOffice 365 & Exchange ArchitectCommented:
Add more servers as source/target to see whether the 2003 server is the bottleneck.

mcnuttlawAuthor Commented:
Deleted and recreated the Routing Group with a cost of 1.  No change in delivery times.

The health check shows only two critical issues on the Exchange 2003 box:

3GB is not set
HeapDeCommitFreeBlick Threshold is not set
Rajith EnchiparambilOffice 365 & Exchange ArchitectCommented:
Do you have a smart host configured on virtual smtp server (2003)?

If so, you need to take it off. Smart hosts should only be configured on smtp connectors.

mcnuttlawAuthor Commented:
No smart host is on Exchange 2003.

There seems to be almost no delay if the queue on the group connector is just a few.  The queue seems to hover above 50 for most of the day which is where the 10-30 minute delay can occur.
mcnuttlawAuthor Commented:
Self solution.
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