Always funny when a website says "invalid email address" for an address I've been using for almost three decades.
@clacke I've had problems when I had en email address with only one char before the at sign. I've also had problems when using a domain other than the normal country TLDs or .net .com .org
@arutaz This one is four domains deep (user domain at Lysator), which is what I suspect is what they weren't prepared for. I used my own .se domain instead, and that worked.