I get this sort of thing constantly because my domain, 3e.org, which I have had for 30 years, is apparently impossible. It's either too short to be real, or starts with a number (obviously impossible).
And like the author, 90% of the time I can just disable their front-end validation and go on my merry way.
And like the author, 90% of the time I can just disable their front-end validation and go on my merry way.