Poor email etiquette.
Just went through a load of emails at work. Granted, it's only the bookies and so email etiquette isn't going to be the first thing you need on your CV, but fucking hell, it's difficult to read a 300 word email that is completely absent of any form of punctuation or grammar.
And it's not just grammar etc, there are so many people who just have no idea how to conduct their tone in an email, I keep reading things like "Do NOT do this" and "you MUST do that." You don't come across as someone trying to be clear and concise, you just seem like a stern c**t.