I notice that most e-newsletters are around the 600-650px width. Is there a good reason for this - OR is there a good reason not to have one the same width of our client's website 850px?
Yes, typically emails are much narrower, because the email reading pane is generally only a small section of an email client, and many people won't open the email into it's own window.
So the narrower it is the more likely it will be read in full, basically, without requiring awkward horizontal scrolling.
Thanks Matthew - could you suggest an optimum width for general usage?
Typically less than 600px would be good - like designing websites in the old days!