Having sent the first campaign, you can now send out a follow-up message to your contact list based on their behavior.
The campaign can be filtered by different criteria:
This way you can send out a few new campaigns e.g. to those who:
1) opened but not replied;
2) never opened
3) opened and replied etc.
When you have the list, you can compose a follow up email and the system will also tell you who has previously unsubscribed, so you do not bother them again:
Having sent a follow-up email campaign, all the emails get linked to the recipients records in NetHunt.