I frequently receive email newsletters that have line after line of links, trying to expose me to everything under the sun. Newsletter authors are better off inserting a context-sensitive link and gently guiding users to a website that incrementally exposes the reader to more and more relevant information. Again, newsletter authors will have to use their judgement in deciding which images are useful and which aren't. A small logo might be fine, in addition to a relevant graph or pertinent photo. But only one or two images is fine.
Images take a long time to load, especially in some email programs.
Good things in HTML newsletters HTML newsletters are more effective than plain text newsletters, and than paper newsletters. The interactivity afforded by hypertext is invaluable and lets newsletter authors trim their works and make them scannable. This guideline is fairly straightforward, but it is important nonetheless. Consider how many emails or other snippets of text the user is likely to read in one day or one session, and remember that they are going to want substance, quickly. If filler seems necessary, then there probably isn't enough content to make a newsletter worthwhile.