Try using following if issue is low disk space on system drive, this will come as a backpressure alert
- Open the following file by using Notepad:
C:\Program Files\Microsoft\Exchange Server\Bin\EdgeTransport.exe.config.
- Modify the following line in the
<appSettings>section:<add key="QueueDatabasePath" value="<LocalPath>" />
For example, to create a new location for your transaction logs at the location “C:\Queue\QueueDB”, modify the QueueDatabasePath parameter as follows:
<add key="QueueDatabasePath" value="C:\Queue\QueueDB" />
- Save and close the EdgeTransport.exe.config file.
- Restart the Microsoft Exchange Transport service.
- Verify that the new Mail.que and Trn.chk files are created at the new location.
- Remove the unused Mail.que and Trn.chk files from the original location.