In our newsletters, we have a header which matches that of our site including around ten navigation links. In the body and footer of the email, there's probably another 15 links. For a don't-get-labeled-as-spam point of view, is that too many links? I had someone tell me that it was way too many but I hadn't heard anything about this before. Our emails are double opt in and are sent out to a list that has grown to around 300,000.
I always look at newsletters and don't really care for them if there is too many links. I would try and keep the number as low as you can. What niche is this for?