post140752.html states
It seems that your email provider was mistaking our messages to you as spam and then blocking them from being delivered. I was able to correct this issue on our end, but if it occurs again in the future you may need to contact your email provider directly. Sorry for this inconvenience.
Also see: general/your-e-mail-address-xxxx-comcast-net-has-a-problem-bann-t13849.html