This was the first song that I can recall hearing that mentioned email in the lyrics. From 2002's Out of Key Harmony, this is the Sinking Ships' You Can't Push Me Away. I am sure there are more songs that make reference to email nowadays, but I'm drawing a blank. And there's probably others that predate this track, I just happened to have heard this one first. Anyone?
From what I understand, this band has been through several incarnations, the other two being the California Oranges (they're from Sacramento, CA) and Holiday Flyer. Looks like they're in the California Oranges mode at this time, check em out on myspaXXX and/or purchase from darla.com.
The Sinking Ships > You Can't Push Me Away