You get about 6 seconds to get your point across in email these days. Some good rules are:
- Write an enticing subject line about 60 characters long
- Add personalization
- Start with a featured item with full-width image, short copy and button (no text link) - the V-shape
- Link the button to your website's landing page
- Continue with a 2- or 3-column news block, with image/short text/button
- Maybe finish with a testimonial or a final news item
- Don't sell, sell, sell everything – give something useful and free
- Schedule to be delivered at the same time across all time zones
And be consistent in your schedule, don't do monthly for three, take a break for six, do one, take a break... stay on track.