Electronic mail systems differ in the manner in which multiple recipients are handled.

In some systems, the originating user agent or mail sender makes all the necessary copies and these are sent out independently. An alternative approach is to determine the route for each destination first. Then a single message is sent out on a common portion of the route and copies are only made when the routes diverge; this process is referred to as mail-bagging. Discuss the relative advantages and disadvantages of the two methods.