I would suggest logging into your Web Mail and checking to see if they ended up in the SPAM Box.... mine is working, so it's not System wide, likely your ISP
I believe that the cause is typically bounced emails which causes the system to suspend any future emails.
Something which might work is to change your email address in the system and then change it back. I believe this would send a verification email and your response to it, would unblock your email address.