Yeah... no it isn't. Blaming people's email servers is the wrong move here. I've used Fastmail.com for the last 5 years, I keep my inbox at 0 and I look at my spam folder every week. I've never had an issue receiving email before. And by the way, over those years I signed up for the beta multiple times. All kinds of wild shit makes it through to my email, so there's no way your invite got bounced. Good luck.