EBS by S.R

July 17, 2008

Outlook 2003 outbound mail delayed for 60 seconds

Filed under: EBS — WITS-SR @ 10:15 pm

Thanks to Mark S. for this fix;

We found that after migrating mailboxes to Exchange 2007, Outlook 2003 clients that were not in cache mode, had all outbound emails waiting for 60 seconds before leaving the clients outbox, however if you clicked on any folder it immediately left.

here is the solution:

Outlook 2003 against previous versions of Exchange Server registers a random UDP port with the Exchange for update notifications.  This means that the client UI is refreshed every time an event fires.  This port no longer registers against an Exchange 2007 server;  instead, Outlook relies on the server’s maximum polling interval setting.  This is set to one minute by default.  The vast majority of installations use cached mode, so they would not normally notice this behavior.  To clarify, the mail in the outbox has been sent and delivered, it is only the client that has not refreshed.

Polling frequency can be increased by modifying the value of


MsExchangeIS\ParametersSystem\Maximum Polling Frequency on the Messaging Server. 

This key has a value of 60000 milliseconds (1 minute) by default.  Changing it to 15000 or even 10000 will gives a faster client refresh time.  The trade-off, of course, will be slightly higher load on the server, but it would be hard to impact performance with <250 users.

 A few notes: 

  • After setting the value (make sure to specify decimal )
  • MSExchangeIS needs to be restarted for the setting to take effect
  • Setting this key is probably an acceptable workaround for a deployment up to 250 users.  Monitor CPU, memory and disk queue length to make sure that they are still at acceptable levels after lowering the threshold
  • would not recommend setting the frequency much lower than 10 seconds. This will result in more traffic to the server, but probably not to an appreciable amount on a gigabit network
  • Real time for the refresh is an additional 2-3 seconds over the polling time because of latency, disk writes, etc
  • Cached mode clients will see that the mail leaves immediately, but there will be a corresponding delay for delivery until the polling frequency is hit
  • This behavior is not present in Outlook 2007 because of its different polling architecture

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