[f2n]

Try using an email address with .wedding or .solutions TLD. Loads of absolutely brain-dead sites refuse to allow them, sometimes they validate by TLD length (all TLDs are 2 or 3 characters, apparently) or other times rejection TLDs they haven't whitelisted.

[rsync]

"(all TLDs are 2 or 3 characters, apparently)"

Which is odd, since there are some very, very old TLDs that are "long" ... I am thinking of .bitnet, .uucp and even the old .ussr[1] ...

[1] "Initially, before two-letter ccTLDs became standard, the Soviet Union was to receive a .ussr domain." (https://en.wikipedia.org/wiki/.su)

[ameliaquining]

Those were never in widespread use in the email era. Anyone who knows about them is already technically sophisticated enough not to make this mistake.