Exchange 2010 Messages Stuck in Retry status in "MapiDeliveryQueue"

In case your Exchange admin life wasn't difficult enough, you can always have this problem, manifested with the following symptoms:

- Mail delivery hung
- Messages stuck in local delivery "MapiDeliveryQueue" with a status of "Retry"

Classic tactics such as restarting the server or right-clicking the queue and selecting "Retry" have no effect.

The key here is that Exchange 2007 and later treat these messages differently than standard SMTP queues. In order to process these messages, they need to be re-submitted using the following Exchange cmdlet:

Retry-Queue -Filter {Status -eq "Retry"} -Server "exchangeserver" -resubmit $true

The default re-submit queue time is 12 hours. To modify this:

1. Using Notepad, edit the file: C:\Program Files\Microsoft\Exchange Server\V14\Bin\EdgeTransport.exe.config.
2. Modify the following line in the section:

<add key="MaxIdleTimeBeforeResubmit" value="<hh:mm:ss>"/>

3. Save the file.
4. Open up the Exchange Command shell and run restart-service *rt