Personally I think it is very important to send typo free emails. But what is more important is how to communicate well about art. Here are a few tips that will help you create a blissful, telecommuting relationship with clients.
#1) When sending my first rough sketch I always include a detailed email describing the item I am delivering, my objective, how it achieves the goals of the project and any questions that have come up.
#2) When writing about a visual element, it's crucial to be simple and clear. For example, it is not clear to say 'the shape on the left'. It would be clear to say, 'the large blue square shape in the upper left corner'. It may not seem like much of a difference but, if you aren't in the room looking at the art with the viewer, trust me they can get confused and may not be looking at what you think they will be looking at.
#3) Before I do revisions to a file I send an email and clarify what I understand the changes to be, and exactly what I am going to do, and when. This simple email, written with precision can save me time later.
My point is, when you communicate to your client over email, take a moment to digest the goal of the conversation, then carefully detail 'What', 'How', and 'When'. Really easy stuff. Not only will it save you time, it will make you money because your client has clear expectations, and you can churn through the work and get onto the next project.