If you’re sending long e-mails with a long feature article or introduction, how many readers are clicking on the subsequent articles?
If the main content is “above the fold,” which means it was in the area of the recipient’s inbox that did not require scrolling, people may not be moving further down the email. Check your click rates by position on the page top to bottom. If click rates drop substantially as you move down the page (and your content is still great), consider shortening your emails to perhaps one topic.
Many people don’t sit at their computer to read email – they just want to get through their email. If you make your newsletter too long, readers might think “Oh, I’ll have to get back to this one” and then forget about it. If you keep it short and punchy, it gives readers the opportunity to do something with your content right then and there. Drive them to your web site with a great story and make sure your site “sticky” enough with more interesting content – and enough pointers to get to it!