There is definitely a phenomenon of checking for prohibited email domains. However, absent extra-functional motivations like user data collection, smart develo

There is definitely a phenomenon of checking for prohibited email domains. However, absent extra-functional motivations like user data collection, smart developers don't bother with heuristics for email addresses much beyond the presence of an '@' character. If you want to know if a purported email address is deliverable, try to deliver email to it.