Even within the same email browser, your email alert or newsletter might function differently, depending on the subscriber's email settings. For instance, a "submit form" button that works properly with the default email settings may be disabled if the subscriber changed those settings to a higher level of internet security.
As a result, it is never good enough to test an email's appearance and function in a single email browser and using single computer. Instead, determine which domains host email accounts for at least 5% of your subscribers. Then, prior to mass distribution, test the function and appearance of your bulk emails and newsletters using the email browsers at each of those domains, while operating from several different computers and a Blackberry, with different internet security settings and screen resolutions, particularly 1024x768, 1280x1024, 800x600, and 1280x800. It's also wise to test your emails when connected to the internet via dial-up as well as a high-speed connection.
This can be a rather mundane process, which is tempting to do half-heartedly. But the consequences of a single error can get magnified thousands, or millions of times, up to the size of your email list.
For quality control, it's wise to develop testing checklists that get signed-off by the reviewer and a supervisor.
