Right now the only official way to enable deletion logging is to use the compact servertask with the -dl option.
After you enabled the deletion logging, each kind of delete is recorded in a central text file on the server.
Unintended deletion of mail is an abnormal operation of Notes Client.
Currently there is no way to track unintended deletion of mail at Notes Client side.
Request to arrange this featur for the future release which will provide information regarding normally and abnormally deletion of the document at Notes Client end.