Types of Opt-ins
To enhance your deliverability and inboxing rates, you must only send emails to recipients who have requested to receive them.
There are various methods to establish if someone wants to receive your emails, but the most practical one is to just ask them. Opt-in may imply different things to different individuals, and there are multiple opt-in degrees.
This page intends to clear the air around the different types of opt-ins you can use in marketing today.