Try looking around, there are plenty of posts about this. This is an answer from Mogura\'s FAQ in the general discussion section:
26. Help! I can\'t type the @ for my username in the game!
For those using Azerty keyboards who are unable to type the @ character, try Alt + Ctrl + 2. If the key combination fails, go in the main planeshift directory and open planeshift.cfg. Edit the line that looks like \"Planeshift.Connection.User =
m_y@email.blah\" to include your email address.