It took me quite a while to struggle with FAS.
issue 1: FAS silently simply does not service some e-mail domains, probably thought of as “throw-away addresses”. But this domain was not of throw-away type. I guess, this behavior is coded in some library, and toplevel FAS people are not even aware of it in terms of being delibarate policy.
issue 2: So then I fell back to my old mail address.
Failure too, and what was irritating was that the error message was misleading. I forgot what it was. Maybe it complained about password or sth. when no password at all would satisfy FAS.
Not really a good first impression. But power users have come to expect these things these days. Also expect that FAS is not fully self-service, i.e. you have to wait 1 day or so until somebody enables things manually.