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Unity 2.4 and slow email & vmail delivery

First and foremost, I'm by no means an Exchange admin/guru. Lately we've been experiencing some peculiarities with our Unity/Exchange email environment I'm hoping someone out there has run into before...<br><br>Environment:<br>- Unity 2.4 Build<br>- Call Manager 3.1.2(c) integration<br>- Exchange 5.5<br>- Unified messaging not yet enabled (to prevent vmail messages from appearing in user's Outlook, duplicate hidden mailboxes exist on Unity servers solely for vmail msgs)<br><br>Last weekend, our organization made the bold move of migrating from the traditional NT domain environment to a Win2K active directory environment. Although the following Monday was a rather painful day, everything seems to have settled down, so we thought. What we've been noticing lately is with SOME users, vmail delivery can talk up to 2-3hr before a message is delivered. It's not a MWI issue. To test, we left a vmail message with the particular user experiencing the delays. The user checked his messages, despite no MWI, and he did not receive it till several hours later. After further troubleshooting, we noticed emails as well as vmails are starting to queue up on the Unity servers-- +500 messages last night. We verified network connectivity, the Exchange admin verified the configurations and Exchange connectivity among all the servers via rpc-pings. We're stumped.<br><br>Strange thing we noticed was, when the Unity server is rebooted, messages start sending--as if it briefly re-establishes it connection to the Exchange mail environment--but eventually hoses up and begins queuing the messages.<br><br>


Re: Unity 2.4 and slow email & vmail delivery

What you're describing is a classic example of an Exchange MTA failure. Just so you understand how Unity works let me explain a couple things.

When an outside caller leaves a message; Unity logs in via MAPI and sends the message from the Unity Messaging System mailbox. That mailbox in homed on the Exchange server that resides on the Unity server. At this point Unity has worked correctly and now it’s the job of Exchange to deliver the message. For that message to get to the other Exchange server it must be transferred by the Exchange MTA. If the MTA is down Exchange will queue the message. Often reboots clear the Exchange MTA.

You might also notice that users on the same Exchange server can send messages back and forth without delay. This is because Unity realized they are a system subscriber when they are leaving the message and logs in to their mailbox via MAPI to send the message as them to the other Subscriber that is on the same Exchange server. Since both mailboxes are on the same Exchange server the message never has to cross the MTA.

OK, so here is the next step. Cisco TAC does not provide support for Exchange MTA issues for liability reasons. Microsoft, however, provides excellent online help at This KB article will show you where to start:;en-us;Q198688


Keith Chambers
Unity Technical Lead
Unified Voice Team, San Jose
Cisco Systems


Re: Unity 2.4 and slow email & vmail delivery

We are having the same problem after pretty much the same scenario. What did you end up doing to correct?