Due to immense spam by bots from email domains matching the pattern *@*
.*.*, we have added an email banning rule for that. Unfortunately, that means some valid email addresses are caught as well (such as yahoo.co.uk) and there doesn't seem to be a way to whitelist email providers in Vanilla (the forum software).
For the same reason, we've also had to ban emails matching *@*
Please, if you want to register, use an email that doesn't match these patterns.