This problem comes up often and at times it is hard to find the solution. If your server has ever had a lot of spam emails you may have had this problem after deleting the mail queue. The problem is that when you purge the mail queue in WHM > Email > Mail Queue Manager it does not just get deleted from the server. It is moved and stored in a file in the root directory of the server. The problem is that you will run out of space on the root drive if this file gets to big.
You can safely clean the comet directory by running the following command. This will remove anything that hasn’t been accessed in more than 3 days.
Run the following command as root user:
You should see something similar to this when it is completed.
******Cleaning up comet for root...Done
That should take care the comet directory. I personally run the file once a month on some servers and others I only run it after clearing the Mail Queue.