I'm a Comcast customer, and even though I don't use my Comcast e-mail
account, I have 2 old e-mails in my inbox from Comcast dating to when I
first obtained my Comcast account. With my Android wifi only tablet's
wifi off and airplane mode on, I was able to open the Xfinity connect
app, tap the e-mail tab on the left side of the screen and see my inbox
with both messages there. I could then tap either message and the
entire message displayed, just as it does for my other e-mail accounts
that I access using the Android e-mail app.
I'm quite familiar with web mail. In fact, when in-town, that's my
usual way of reading/sending e-mail. All my e-mail accounts can be
accessed web based via any browser when logged into a wifi signal. None
of those accounts can be accessed much less read when I'm off line.
Doesn't seem to me that the Xfinity Connect app provides a "web mail"
user interface. Once on the email tab of the Xfinity Commnect app, the
user interface is very similar to the android e-mail interface - at
least on my Samsung tablet.