As if information overload weren’t enough to handle on its own, we are expected to also keep track of how to spell and abbreviate all of the digital devices and services we use. There is no “e” in Tumblr or Flickr, iTunes is never capitalized but MacBooks are, and so on. It’s complicated, but at least they are proper nouns.
What about electronic mail, clients ask me. Is “email” or “e-mail” correct? I would forget about being right and focus more on being appropriate to whatever context you’re writing in.
Mignon Fogarty (AKA Grammar Girl) mentioned the email v. e-mail debate in 2011, ultimately calling the decision “a style choice.” She notes that while many of the publications native to the web tend to lose the hyphen, others, like the New York Times, still include it. Ultimately “common usage” favors email, but keep in mind that those who are less “permissive” still prefer the hyphen (additional examples here).
So use your judgment — how formal is your communication context? — and make sure to be consistent with your choice. The only way to really go wrong here is to switch between the two within the same document. Consistency is key.