How does the system handle opt-outs
Email inboxes are sacred -- and sometimes people just don't want to get valuable emails (oh well, their loss ;)).
Your end-user can easily opt-out of receiving your emails by unsubscribing from the link found at the bottom of the email.
When they opt-out, your system automatically grays them out on your contact list and they won't get any messages from you moving forward.
Now, let's say they change their mind. (because FOMO, as the kids are calling it these days)
Unfortunately, you won't be able to manually re-subscribe them. You can view their customer profile to see any history, but they'll have to re-subscribe on their own.