Online Status Server Code: "ALERT SERVER MESSAGE". "TEMPORARILY BLACKLISTED IP ADDRESS - TRY AGAIN LATER"

I travel to Portugal frequently for business.  Whenever I try to access my Xfinity email I receive the blacklisted IP address message.  Sometimes the block takes a week to be removed and other times it never gets resolved before returning back to the USA.  I am here in Portugal again and I still have this persistent problem.

I use NOS, one of Portugal's major communication companies as my Wifi provider.  I've contacted NOS for assistance and they said the problem emanates with Xfinity.  Do you have any advice as to how I can rectify this very annoying problem?