A lot is going on within your inbox, usually more so than a website. Several window panes may be visible other than the obvious email listing, like editor and tools bars, menu items along top and side, calendar and scheduling information, and then maybe the email viewing pane, often a small portion of the display space down at the bottom corner. Your email will be competing with other input, even the reader's real work.

This aspect should affect the way you intend to become noticed, and first and foremost keep in mind your email is invading someone's personal space. So develop a newsletter that first tells who you are, why you're sending the email and what it's about, even before the reader loads images. You'll have more success with your recipients opening your email in the first place or coming back to it when they can.

Additionally, it may seem counterintuitive, but allow your readers to see an unsubscribe link close to the top without having to load images (I know it's hard, but trusting your readers will pay off in the long run). Many organizations now place this link in the fine print and this may be what you ultimately decide to do; it must be included somewhere. But my suggestion is to let your reader easily unsubscribe rather than spam you.

Many email clients have now made the spam button very easy to access, along side other important buttons like "Get Mail", "Compose", "Send", etc... If readers don't want your email, then might as well let them see right away how to unsubscribed, or they are more likely to click the spam link within the email software to get you out of the way, especially if they can't find your unsubscribe link right away. Too many spam reports is not good for your email newsletter efforts. Unless you're a well-known national or regional organization where email clients know you'll have a higher volume of spam, spam will only hurt your relationship and trustworthiness with email clients, reducing your chances that your email newsletter will actually be delivered to your continued faithful readers.

Other layout and planning suggestions:

Know what you're content and design will be focusing on first - make that the obvious highlight within the top of the newsletter.

Not always, but generally, subscribers will be more receptive to shorter emails than one that tries to tell all with one shot - send them out to your website to read more if they want.

Write a subject line that will not only tell them what the email is about, but is creative, fun, and interesting approach to the subject.

Test when the best days are to send your newsletters.

Even ask your subscribers within signup forms and surveys how often they would like to get your newsletter.