Surely it's exactly why you might ask that — admittedly as a semi-trick question, which you should probably only direct at experienced people who really ought t

Surely it's exactly why you might ask that — admittedly as a semi-trick question, which you should probably only direct at experienced people who really ought to recognise it as such. Email validation is a problem with a lot of plausible answers — many of them wrong — so it has the potential to be quite a good discriminant (depending on whom you're trying to hire, of course).