not secured

If you are asking about webmail ( https://connect.xfinity.com/ ) the warning is generated by your web browser and is due to the way most current browsers are designed and the content of the emails you view. Whenever you use any provider's webmail to open an email that references a non-secure (loaded with "http" instead of "https") image, script, or other item, the browser warns you. In webmail, this probably happens most often if you have the setting for "Allow pre-loading of externally linked images" (gear icon / Email Settings / Security / Mail) checked. If you don't have that option checked, you're probably getting the browser warning when you open an email that has insecure content and you click the "Show images" button.

Sadly, many of the emails Comcast sends have insecure image links and will trigger the browser's warning. Two examples are "http://log.dmtry.com/" and "http://xfinity.comcast.net/favicon.ico". To a browser both of these are "insecure" because they use "http" instead of "https".

A secure web page that loads insecure content is said to be using "mixed content", and may be subject to a "man-in-the-middle" attack. Comcast seems to think this is not a problem, but Internet security experts think otherwise. See https://www.google.com/search?q=mixed+content+pages+MITM.

Great information as to why not secured shows up. Glad you mentioned MITM which I never knew about. Thanks to you detailing "not secured" I'm able to further research to find a resolve.