Email Shows "Read" But not "Delivered"

In some instances, an email may show as read by your customer but could be reported to you as not delivered. 

The reason for this discrepancy is most likely the result of one of two things.

1. Your customer has virus/spam checking software loaded and set up on their email that scans the email before delivering it to their inbox. This type of checking software will cause the email to be reported as read.
2. Your customer is using a program such as Unroll.me which takes all their emails and filters them into a single email and stores them for them rather than delivering them to their inbox. 

If you go to their contact page and scroll down you will see two boxes

Emails sent - will list all emails they have ever been sent to

Activities - will show all activity connected to them including when emails were sent, opened, and if links were clicked on.