Mail notifications are duplicated when using Microsoft Exchange Server
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Problem
When users receive notifications from Confluence, those notifications are duplicated, sometimes more than once. The content of the emails are identical.
There are no errors in the application log, and increasing the SMTP timeout in Confluence does not resolve the problem.
Diagnosis
Environment
- Microsoft Exchange is being used as the Mail Server
- There are no significant queues from mails from Confluence
Diagnostic Steps
- Try setting up another temporary Mail Server, such as Gmail to see if the problem persists
- Try enabling protocol logging on the Exchange Server
A test environment is ideal for both checking the problem is reproducible, and avoiding disruption to production instances
You may see the following message in the SMTP logs from Exchange:
2016-03-30T02:54:52.036Z,SERVER\Relay from Location,08D33F1F53A90D4C,23,x.x.x.x:25,x.x.x.x:60327,*,Tarpit for '0.00:00:30.935' due to 'DelayedAck',Expired;TimeoutCause
The tarpit message in the logs indicates that the logs have been delayed - causing the message to be retried (and then submitted to the queue).
Resolution
The MaxAcknowledgementDelay value must be set to zero. First, verify the current status by running the following command in the Exchange Management Shell:
Get-receiveconnector “connector name” | fl sort-by *max*If the value for MaxAcknowledgementDelay is greater than zero, use the following command to set the value to zero:
Set-ReceiveConnector "Default connector (Servername)" -MaxAcknowledgementDelay 0Credits
The source for this knowledge base article can be found at the Exchange Gloves Blog.