Comcast likely has gone to something like this...
Turn Your Access to Third Party Email Programs On/Off in Xfinity Email
To provide our customers with additional security, we added a new checkbox to the Xfinity Email website. This may affect your ability to manage your Xfinity Email (Comcast.net) through third-party programs like Outlook, Google, Apple Mail, Thunderbird and more.
These programs could expose your Xfinity ID and password to fraud and other risks, including the potential for external programs to read, download and delete emails on your behalf.
If you currently use a third-party program to read your email, the security setting is checked by default. If you don’t currently use a third-party program, the setting is unchecked and you won’t have access to these programs. You can easily change this setting at any time by checking the box and turning on access. Here’s how.
How To Update Email Security Settings
Sign in to Xfinity Email using your Xfinity ID and password.
In the top-right corner, click the Gear icon, then select Settings.
Click Security.
Uncheck the box under Third Party Access Security to prevent third-party programs access to your Xfinity Email, or check the box to allow access.
FAQs
Can I still access my Xfinity Email account (Comcast.net) through a third-party program after I check the security box?
Yes, you can manage your Xfinity Email through third-party programs when the Access Security box is checked. If this box is unchecked, you’ll receive an error message when you try to set up your Xfinity Email through a third-party program.
We recommend accessing your Xfinity Email from the Xfinity Email website.
Will this impact me if I have third-party email on my Xfinity account?
No. If you already have a third-party email on your account for verification purposes, you won't be impacted.
What will happen if I don’t disable third-party access?
If you continue to access your Xfinity Email account through a third-party client, you may be more susceptible to potential credential fraud.
Will changing the email security settings affect how I receive emails or manage my mailbox?
If you don’t have the Access Security box checked, you may receive an error message when you try to set up your Xfinity Email through a third-party program. This is the only change you may experience.
https://www.xfinity.com/support/articles/third-party-email-access
