This should help you understand better our email provider SendGrid and how to measure the effectiveness of your updates.
Just sent an update and want some more information on the statistics we offer? To track email statistics in updates we rely on our email infrastructure provider (SendGrid).
Due to the nature of email the stats we get are not 100% accurate in some cases, accuracy of tracking greatly depends on the recipient's email client, whether the recipient chooses to load images in emails, etc..
To find out more about open and click tracking check out these sources: