An easy way would be to use program membership.
Make everyone a 'member' of the program. Once the email is delivered, change the status to 'sent'. Anyone who is suppressed will remain 'member'.
An elaborate way could be to:
- Create a Smart List with your targeing called 'Smart List - Audience'
- When sending an Email X, use Smart List - Audience as an audience
- Create a 2nd Smart List called 'Smart List - Suppressed' with member of Smart List - Audience AND not was sent Email X
Both wouldn't couldn't the occurences, but it will give you more insight than you have currently.
It's done already, but still dependent on the way the program are set up, so not ideal. Furthermore, I often have to step in on Marketo instances that we have not set up and that have been in production for a while and in this case, it's usually far too late
Figures that you'd have tried that. I know of no other way to check who was capped by the limit.