I will try to explain my situation as good as possible:
We're going to do a webinar and I sent an invitation mail this week, on the 9th of January.
I created a report with the Email Performance and it says that it was sent to 12.266 people and was opened by 1.986 people. So there are 10.280 people who didn't open the email (see screenshot attached: Email report).
Now I would like to send a second invitation mail next week to the non-opener.
I created a new Email program with the following filter in the smart list:
1. Was sent email
2. Not opened email
(see screenshot attached: Smart List)
Now I checked the audience of the 2nd mail and it says that it will be sent to only 9.499 people instead of 10.280 (see screenshot attached: Audience).
So there are around 700 people missing.
Do you know where this comes from? Should I add any more filters?