Why is my newsletter open rate so low?

Click-tracking software puts an invisible pixel at the end of the newsletter template, but Gmail will partially hide your email if the content is too long and require the user to click-through in order to download and see the rest of the message, therefore never triggering tracking for emails that were not fully opened. If you have a newsletter and are seeing very low click-through rates, this might be the case, and your solution is to redesign the template to fit within Google's limits.