Discrepancy in email campaign results

Kelly, I see this happen sometimes as well. I believe it's because of the way certain email programs work. For example, in some cases, a person may just view an email in a preview pane and not actually open it. They can still click that email but the open might not register.

There is actually a better explanation that mine in this discussion thread: http://community.marketo.com/MarketoDiscussionDetail?id=90650000000PcE0AAK

If they're viewing it in the preview pane, that will trigger an "open".  The only time this won't register an "open" is if they are reading it in plain-text mode or they have images turned off.  So what's happening here is the user has viewed/opened the email in one of these two instances and has clicked on the tracking link in the email that registeres the "click".

Microsoft Outlook 2007, 2010, 2013 have images "off" by default for HTML emails unless the sender is a trusted address (white-listed) or the user has otherwise specified that it is OK to display images from that particular sender. Marketo knows an email has been "opened" via small embeded image. Whether or not a recipient views the message in the preview pane or in full view, if the images are disabled Marketo cannot see that a message was opened. However, that recipient may still click a link, hence you would not see an "open" from that recipient, but you would see a "click" and web activity.

This is why I put much more emphasis on click and conversion results of A/B testing than I do sheer open rate.

Example: I just received the message below from Shutterstock. The images do not display by default, but I clicked through. They will read a click with no open activity for me for this message. This message also demonstrates why emails consisting entirely of images is a bad idea.

Thank you all for your responses. This is very helpful!