Perhaps ask comcast why they blocked you on that IP address. Note this well. The IP address used by your desktop computer is allocated by the provider of the internet service. That used by your phone is allocated by the phone service provider and they can not be the same. So the fact that you are blocked on one and not the other is basically not relevant here as the error is about a specific IP address. But I am confused are you just starting using Thunderbird with that address? Or have you had an issue and erroneously tried to fix it by adding the account again?