People can also incorrectly type in their email in a way that looks fine, so I'm skeptical of intentionally not allowing valid email addresses just to cut out a

People can also incorrectly type in their email in a way that looks fine, so I'm skeptical of intentionally not allowing valid email addresses just to cut out a small fraction of those. The isemail.info site recommends a warning if it doesn't look right, but allowing the user to override and use anyway, which seems sensible to me. (I say this as the proud owner of a lastname.email domain, where the .email TLD was made explicitly for this 8 years, and I still have problems with bad validation.)