It looks like this same issue was preventing me from receiving my forum account activation email.
I tried to sign up last night with hotmail.com, but never received the email. I had it resend last night and again this morning, verified nothing in spam, still no activation email.
After work, I changed it to my vfemail.net email address, and I never received anything there, nothing in spam, either.
A while later, I changed it to my gmail address, and I got my activation email right away. So here I am.
If I had seen this thread before, I wouldn't have bothered with hotmail (same as outlook.com) in the first place. But, vfemail.net had the same problem.