Mail Delivery Slow to Exchange 2010 Mailboxes (Co-existence with Exchange 2003)

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We recently installed Exchange 2010 (1 CA/HT server, 2 Mailbox servers), and currently have a co-existence with our existing Exchange 2003 server. At this time, only a very small percentage of user mailboxes (<1%) have been moved to the 2010 server, as we are still testing to ensure proper operation. What we are noticing is that the users who have mailboxes on the 2010 server are getting a substantial delay upon receiving mail, anywhere from 1 to 20 minutes, seeming independent of message size or source (internal or external).

Based on what I can tell from the message tracking information, the message gets delivered to the 2003 server first, and then is routed to the 2010 server, which is where the hangup is. What I am unsure of is, (1) why is the message not delivered directly to the 2010 server and (2) why is there such a delay in this routing?

Messages being sent " from" the 2010 users appear to route just fine, and show up instantly in the mailboxes of the 2003 users. SMTP send connectors have been set up on the 2010 server seem to working correctly.

Also, when checking the queues on the 2003 Exchange server, the default Routing Group Connector between the 2003 and 2010 servers has a constantly fluctuating high number of messages in it, with a size ranging anywhere from 5,000 KB to 4,000,000 KB. Given the small number of mailboxes we currently have residing on the 2010 server, I'm sure this isn't standard mail traffic. Could this be caused by Public Folder replication process of some kind? Could it be the reason behind the latency in mail delivery for the 2010 users?


Ed Crowley [MVP]

It could, but nobody can say for sure without knowing more about the messages in those queues.Ed Crowley MVP " There are seldom good technological solutions to behavioral problems."


It could, but nobody can say for sure without knowing more about the messages in those queues. Ed Crowley MVP " There are seldom good technological solutions to behavioral problems."
As far as I can tell, I can only see this connector via the Exchange 2003 ESM. When I attempt to view the messages in the " Routing Group Connector" between the 2003 and 2010 server, the ESM window " locks up" and never displays any messages. The message count is usually anywhere from 100-200. I've tried searching to find out if this behavior is expected or normal, but haven't had any success in finding out what is causing it.

Ed Crowley [MVP]

That is not normal. It could be caused by public folder replication, but I can't say without knowing what's in the queues.

Ed Crowley MVP " There are seldom good technological solutions to behavioral problems."


I was finally patient enough to allow the queue contents to load (I just let it run for about 30 minutes).

Basically, the queue is full of messages with a status of " Retry" all from " [2003 Server]" all going to a public folder database on one of my 2010 mailbox servers. I have a public folder database set up on each of my mailbox servers, however all the messages appear to only be directed at only one of them, for what it's worth.


Also, every " message" in the queue is exactly 110,993,302 or 111,235,662 bytes in size.

Ed Crowley [MVP]

That reads like the kind of thing I'd call Microsoft Support about.

After posting that, I had a brainwave. Check the message size limits at every place along the way. I'm wondering if you're getting all those resends because there's a message restriction that's causing those messges to be repeatedly resent.

Ed Crowley MVP " There are seldom good technological solutions to behavioral problems."

Gulab Mallah

Make sure that your exchange is not open for Relay!

Do you have ForFront Sercurity for exchange or any third party application installed on the server?



Those messages are the public folder replication messages. Increase logging for replication and look at any events. Are you on Exchange 2010 SP1?

Also, what version are your clients?


The Exchange server is open for relay, but only to specified networks.

I'll check the logging. Exchange 2010 is SP1, and the clients are all Outlook 2007.

Novak Wu


Is there any Event Log error after increasing logging for replication?

To troubleshoot the issue, please also try the following steps.

1. In Exchange 2010 server.

a. Check permission on Default Receive connector and checked Anonymous users permission.

b. Create a proper SEND Connector on E2010 Server

2. In Exchange 2003 server.

a. Check the Default SMTP Virtual server properties and if SMARTHost is there then remove it from there & Add the SmartHost on the SMTP and Send Connector

b. Click Default SMTP virtual server -->properties -->Access Tab --> Authentication --> check Anonymous Access , Basic Authentication & Integrated Windows Authentication

c. From Exchange System Manager delete the Routing Group connector under Exchange 2003 & Exchange Administrative group

d. Recreate Routing Group connector under Exchange 2003 Administrative group for both ways.

e. Run IISRESET on Exchange 2003 server and restart the Transport service on Exchange 2010 server.

However, if the issue persists, please also refer to the following article to create an additional RGC.

Hope this helps.

Novak Wu


Big thanks to everyone who has replied!

I have tried just about everything suggested here and what I could find just searching on the web myself. It's quite frustrating. From what I can tell, these messages are moving, but only after sitting in " retry" status for some time. Message delivery to mailboxes on the 2010 side is still substantially delayed. Re-creating the RGC appears to do nothing more than move the stuck public folder messages to the new connector. Unfortunatly, this is obviously delaying our transistion to Exchange 2010, as we obviously can't start moving mailboxes over until this issue is resolved.
To summarize:

Exchange environment with 2003 and 2010 servers co-existing

Mail sent FROM users with mailboxes on the 2010 server(s) is routed fine

Mail sent TO users with mailboxes on the 2010 server(s) takes anywhere from 5-20 min to be delivered from the time it is received by the system. Mailboxes on 2003 server get instant delivery.

Message tracking shows the messages arrive at the 2003 server, then be queued for transfer to the 2010 server for delivery, which is where the delay is occuring

Routing group connector between 2003 and 2010 server shows a fluctuating number (~100 at any given time) of messages stuck in " RETRY" status, all from the 2003 Information store to the public folder database on the 2010 server, which appear to eventually clear out of the queue, but not until after being retried up to 6 or 7 times.

All checks and steps outlined in this thread so far have been done/verified, including re-creating the RGC.
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