I'm looking at a campaign/flow and see that some recipients were skipped. Why were they skipped?
In a campaign or flow's overview page, you can navigate to the recipient activity tab to see all the information about the contacts who were potential recipients for a particular campaign or flow. This will show you who received it, who opened it, who clicked in the email, and if anyone was skipped. This is where you can find the reasons why someone was skipped. Some examples of why a recipient could be skipped are smart sending, a user is suppressed, the recipient's email address was invalid or, specifically for flows, they may have failed a flow filter. This last example will show exactly which flow filter skipped that recipient.