Comcast email does not work with third party email clients-except on home wi-fi.

After 20+ years, my comcast email accounts will no longer function on any wifi networks except my home xfinity network.  I have different ISP's at my vacation home and offices, where comcast services are not available.  Comcast's "easy" answer is to use their webmail on the website.  That service is clunky, cumbersome to sign into, and not convenient for anyone that needs to check email frequently.  

Why is this now a problem?