What?!? You gave me a username of robertan, nobody calls me Roberta, it's Bobbi!
Whoa ... breathe. Your username is used to identify you with the Radke Land servers, and I promise, they're not judgemental! You can have (within reason) as many aliases to your username as you like! For example, my username on the Radke Land servers is josh. If I went out job hunting, it might be prudent to have a stuffier email address, like Joshua.Radke@radkeland.org. The process of setting this up is trivially easy, so I encourage you to ask for as many aliases as you think you'd like (please don't get carried away!).
You can then configure your email client (the option will be named something like "Reply To:", or "Display As:") to show your alias. Email to any of your aliases will go to the same place as emails to your machine username.
For now, is is unlikely that there will be any 'clashes' for aliases. If you really want an alias that someone already has configured, I'll hook you up with the person who claimed it first, and perhaps you two can work it out. I suppose I'll have to work out a dispute system someday, but let's just play nice for now.