This is usually due to the user not having the correct user profile permissions and can be rectified by following the steps below.
Check that you are permitted to delete Incoming Mail tasks.
Enter the User Profiles program.
Select the User, and click UPDATE.
Select the Authorisations tab.
Navigate to the Task Deletion area.
Tick Delete Incoming Mail (case) and Delete Incoming Mail (task list).
Click SAVE and EXIT.
The user will need to log out of Proclaim and back in to pick up the changes.
If you or your System Administrator does not have access to User Profiles, please raise a new case online and reference the title of this article.