When trying to activate the trail for Start10 as I am an owner of Start8, I tried to use my existing account email address which is an Apple @me.com address (and the same as the email address on this account) No emails were received. I tried the mac.com and iCloud.com variants with the same results. And no, there are no messages sat in the Junk folder.
In the end, i had to use my work email address to get an activation email, so I have the trial activated but if I decide to upgrade then I'm concerned that I won;t be able to activate again.
So primarily, the question I have for you is ... Is there an issue with Stardock email being sent into Apples email systems? Are they being bounced?