I ended up giving up on that after one too many websites rejecting my custom domain (which I’m the only one using) on signup. These lazy / ignorant colleagues are annoying -_-‘
No idea what sort of security this is supposed to provide.
They probably see it as some sort of security / anti-spam mechanism.
My emails have a tendency to become spam filter bycatch, to the point that when I was job hunting last year I'd have to ring people after I sent them my resumes etc. to confirm they actually received my email.
And when I give people my email address, I usually have to assure them that steve@stevetech.xyz is a legitimate email address and not a joke (it's not actually steve, but you get the point).
Definitely would not recommend using it for your personal address.