It's a little hard to explain. Part of our mail server's features (we run our own mail/webserver) is that if the part before the - is legit and the part after the - doesn't exist, it sends the mail to the person before the -. It is useful for keeping track of who is giving your address out to marketers/spammers. I know that 3FC would never do such a thing but it is just a force of habit to register to websites that way now. For instance of my address was email@example.com
and I registered with amazon.com, I would use firstname.lastname@example.org
. Then if I got an email from Joe Spammer address to email@example.com
I would know the only place they could have gotten my address was from Amazon.com. Make sense?