So what is the difference between Marketo's IS vs. IS NOT vs. Inactivity filters? Without a clear understanding of what each filter represents, it is difficult to chose.
This quick breakdown of what each filter does to help you understand what results you'll see when applying them in logic.
“IS” and “IS NOT”
IS will match anything exactly to what you would like to filter.
For instance: Email address is: firstname.lastname@example.org. Using the “is” filter will find anything that matches exactly. (Be sure to select carefully when making this selection. It is easy to overlook an error and Marketo will not make suggestions for uncommon field values or for specific data in a field.)
IS NOT will exclude anything exactly, the same as above, but opposite.
Inactivity filters should be used when you are looking for an activity that did not happen, like "did not open email," "email did not bounce." Inactivity Filters can be found at the bottom of the filter list.
Here is a list of outcomes when using Is, Is Not and Inactivity filters for "sent an email."
1. Was Sent Email –> Is –> Original Email
Was sent email that is the original email
2. Was Sent Email –> Is Not –> Original Email
Was sent ANY email that is not the original email
3. Not Was Sent Email –> Is –> Original Email
Was not sent original email, but could have been sent any other email.