Do what you can to make your email go into your customers' inboxes. You must work to get your email to pass ISPs and not get tagged as spam messages. If they get tagged as spam messages, your recipient may never see them. Check with customers to see if they are getting your emails, or if they're no longer interested.

While extra graphics and other things that can easily be blocked by filters are unnecessary and detrimental to your campaign, your company logo does need to be included...