There are a couple of real gems in there worth considering, including this one:

Remember that “Text Language” is for texting only! Sure when you’re limited to a few characters it makes sense to abbreviate and use acronyms; it’s a part of texting culture. But don’t forget Grandma won’t understand it when you respond to her joke with LOL.

The same could easily be said of making sure your email copy is understandable to your whole audience if your list covers a wide range of demographics. After all, you don’t want to alienate certain edges of your customer base by talking too much about, say, your memories of the William Taft presidency when most of them are concerned with the latest episode of Hannah Montana.