Will Having Unmatched Emails Prevent 2nd or 3rd Attempts From Going Out?

Generally, no. Unmatched emails will not prevent follow-ups from going out. However, you can choose to block follow-ups when you have unmatched emails by going to the project in question, and clicking the Settings button to the top of your screen and clicking Project Settings (You can also access this screen when you are viewing the All Projects page by clicking on settings for the specific project).

Once in the Project Settings screen, you can click the blue Advanced Options to enable more settings to be shown. You will see a setting called 'Block Follow-Ups'.