Webmail ( connect.xfinity.com ) is v7.10.3-0-78. The app for Android and IOS is v7.7.1.
If you got an email saying you should update, check the message with Comcast's webmail and look for the XFINITY Verified Email logo next to any message that claims to be from Comcast/Xfinity. See https://www.xfinity.com/support/articles/comcast-verified-email. If the logo is missing when you view the message in webmail, the message is not from Comcast.
Unfortunately, AFAIK the logo is not present when you view one of their messages in an email app or program, not even in Comcast's own email app. It's only visible when you use their web email site.
The information provided by @BruceW is correct. The link he provided will show you the Xfinity Verified Email logo, which indicates it's officially from Xfinity. Please let us know if there's anything else we can help with.