Creating an Opt-in Email
I would like to confirm permission from my client's contacts list. I envision to send an email asking the contacts containing a checkbox/button to confirm each individual contact's interest in subscribing to the mailing list.
I've tried googling how I can create opt-in emails but can't seem to hit the right keywords to get the answers I need. Could you please guide me on how I can set up something akin to what I have envisioned? (Checkbox/button upon ticking/pressing will register the contact's confirmation to the emailing list)