I just received an email from "Email Administrator" firstname.lastname@example.org claiming my comcast email box is full and that I must upgrade my email box by clicking on a link "upgrade your e-mailbox here". Is this a trick of some kind? If so, what is it?
@msavin wrote: ... Is this a trick of some kind? If so, what is it?
Yes, it's a trick. It's a phishing email, a scammer attempt to steal login and account information. If you check your email with Comcast's Xfinity Connect webmail, 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).
Please see Comcast Email Phish or Legit? How to Tell (and rules for posting) for more information about identifying, reporting, and posting phishing emails. The article is somewhat out of date, but still useful.
Samples of recent phishing messages can be found at http://constantguard.comcast.net/help/alerts under "Top Phishing Scams".