The phrase that makes this thesis statement wordy is: electronic mail.
Explanation:
Wordiness refers to making something longer than it should be, that is, using too many words to express something. In the case of the thesis statement we are analyzing here, all words seem to be necessary with the exception of the final phrase. As we know, "electronic mail" is no longer an expression in use. It's been decades since it has been replaced by the shorter version "email", "e" standing for "electronic". Not only does using "electronic mail" make the sentence wordy, it also makes it sound old-fashioned.
