If users block a pending email and set the corresponding email campaign to inactive, the email will still exist in the Blocked Emails tab.

Because the system doesn't need to send out the blocked emails, the system won’t check whether the corresponding email campaign still exists or whether the status of the campaign has been changed.

Nevertheless, if unblocking the same email, the email won’t go back to the Pending Emails tab. It will disappear completely. 

This is because the system will send out the pending emails. Before the system does so, it will check whether the corresponding email still exists and whether the campaign status is Active.