Incoming email problem with certain mail

I recently tried to create accounts with Microsoft and Apple and in both cases the email needed to verify the accounts never showed up in my email or even my spam folder. However, when I created my Norton account, that confirming email showed up in my mail within moments. I’m running the most recent Internet Security with Windows 7 and Yahoo email service (sbcglobal.net). Is it possible that the other confirming emails were somehow blocked by my firewall? If so, what is the solution? To the best of my knowledge, all other email is coming through fine.