If you tell Mail-It to „leave mail on the server“ so that you can check your mail again from another machine, you’ll still probably want to delete some messages permanently, so you don’t have to deal with your spam twice.
In some email apps, just deleting the message and then checking your mail again will cause those deleted messages to be deleted from the server. What many people fail to realize about Mail-It’s method, however, is that it’s not enough to just delete the messages — you have to actually empty your Deleted Mail folder and then check your mail again to have those messages removed from the server.
So if you’re on the road and want to get rid of messages for good, remember to pull down File | Empty Deleted Mail Folder and then check your mail again as the last thing you do before returning to your other machine.