Unregistering Exchange servers from Symantec Email Submission Client
You can unregister the Exchange servers that are associated with the Email Submission Client for a clean uninstallation. If you do not unregister the Exchange server, uninstallation of Email Submission Client is not clean and submission folders are not removed from the user's mailbox.
To unregister Exchange servers from Symantec Email Submission Client
In the Symantec Email Submission Client user interface, select the exchange servers that are listed in Enabled Exchange Mailbox Server that you want to unregister.
Click Remove or Remove All.
Ignore the At least one mailbox server should be selected warning.
Click System Update and select the Exchange servers that you have unregistered.