email “from” setting

Sorry if this has been discussed already… After searching Support and the Codex, I couldn’t find any answers. Could be it’s something so stupidly simple that no one has needed to post about it.

I set up a blog for my wife’s restaurant http://www.raddacaffebar.com. All seems to be working well enough, but when a new user registers, the email they receive is coming from “World Wide Web Server”. It’s the default email from my Xserve. I can’t find the setting in Admin to tell WordPress what “from” info to use.

TIA, and sorry if this is an old topic.