Messages are not physically deleted until you save the RMAIL file, or explicitly request that marked messages are expunged. See below for details.
Choose Mail > Get New to get any new mail that has arrived for you. You may have to tell the environment where your system's mail mover program is in order for this command to work properly. See Moving mail into your RMAIL file for details.
Choose Mail > Save to save the current RMAIL file. This physically deletes any files which you have marked for deletion, as well as saving information such as which messages have been answered. Once you have saved the RMAIL file, deleted messages are no longer available for undeletion.
Choose Mail > Expunge to remove any message from the RMAIL file which have been marked for deletion. This command is very like Mail > Save , except that only deletion operations are performed.