When I was an undergraduate student at CMU, the email systems supported fuzzy common name matching, so even though my Andrew username was
jrc, you could email e.g.
firstname.lastname@example.org and it would try to deliver that (if unambigious). If you added a plus sign (
+), the system would do an exact match instead of a fuzzy match, so in practice my email address was
email@example.com. (Note: that is no longer my email address.)