Test the marketing newsletter with other email clients

If you have found a newsletter format that is easy to read, grabs the reader's attention and makes them click through to your site, that's no reason to celebrate and lean back contentedly. First you have to test that layout in as many email clients as possible on as many platforms as possible.

Don't forget about Web-based email services like Hotmail or AOL or Yahoo! Mail or Rediffmail.

Make this layout and rendering test a routine.

Whenever you make a change to your newsletter template, test it. The smallest changes can have the most surprising effects.