This is indeed an annoyance that we noticed as well. Send me a message at jean [at] blendle.com and I'll get this sorted.

If you're using gmail, the + alias seems to work for signup.

https://support.google.com/mail/answer/12096?hl=en

That's really not the issue. Yes, I immediately used an email alias to bypass it, but that doesn't stop it from being a common and annoying issue with these types of access programs. I think of it the same way as people who kickstarted a product being told they're not getting access until a bunch of other people that signed up after it was fully funded.

I heard that email addresses are not particularly hard to come by.

They seem to be filtering certain email providers. I tried to sign up with sneakemail (a paid email service) and the reg system told me "Please sign up with your personal email address." - when I entered a password. :-(

Could you not just use another email address?