Kind of related: I have a 'firstname@lastname.email' email address. I had booked movers online as I am moving apartments. I thought it was confirmed because I got an automated email back confirming the booking. I gave them a call about a week later to double check everything was OK and it turned out they never booked me in because they thought it was a fake address ("Wow, this is really weird, I've never seen an email address like this").

Luckily, they could still book me in but at a different time slot...