Temporarily blacklisted IP Address

Hello,

I have had my Mac for almost 5 years. The first few years, my email worked great on the Apple Mail app. Now, I cannot get mail on my computer. I am constantly seeing the error message with a triangle and an exclamation in the middle. When I click it, it says "The following alerts are from the IMAP server for “Comcast”: Temporarily blacklisted IP Address - try again later." This has been like this for a year and I've tried trouble shooting everything with different port numbers, VPN, etc. Can you please help me resolve this? It is incredibly frustrating! The emails that are not working are [Edited: "Personal Information"] and [Edited: "Personal Information"]