What is the enhancement in mind? How should it look and feel?
I have alts on other accounts.  Instead of using space by adidng them to my friends list, I would like to be able to add them to the list maintained by EasyMail.  I used to use another addon called SendSelf with Easymail to make this work, but SendMail is not working.  Would be nice to have this feature in EasyMail.
I would suggest adding the option to add/remove Alts to the Blizzard Interface Addon screen for Easymail.  Don't validate the alts names.  You could also add it to the easymail mailbox dropdown list that shows the alts with "Clear Field" entry by adding a "Add Character" entry.
Please provide any additional information below.