Using generic metrics for gauging success is very common in email marketing.  Specifically the most common gauges are:

• Open rate
• Click rate

Don’t misunderstand, these metrics are important but for most email campaigns they should not be the defining factor in measuring success.  Success depends on the intent of the email.

Here’s an example, an email campaign that consists of one communication promoting an event and a second that offers informative tips.  The open rate matters in both cases as it is an indicator of subject line clarity and recipient loyalty.

In fact, for the informative tip the open rate is a good immediate indicator.  However, the rate of the email being forwarded might be a better gauge because it clearly indicates that recipients valued the content.  Even a fairly small percent of forwards is a major victory because this particular metric typically only records a fraction of actual forwarding activity.

For the event promotion opens are a good initial indicator and click through rates are important.  However drilling down to what was clicked on is typically more important.  Were people drawn to a video link, an image, a headline, or a particular hyperlink?  This information is a better gauge for success because it can be linked to who registered for the event as well as inform future communication on what draws the target audience.

Of course this is only a sample and other metrics would be more critical to success in other cases.  The point is that open and click rates are usually a starting point to evaluating a campaign.  They rarely are capable of being a stand-alone gauge for success.