The way a user enters a relationship database is very important to define their quality and lifecycle. Customer relationships develop better when we take care of how we constantly send our marketing communication to them. Opt-In and Opt-Out deal precisely with the aspects of entry and exit of this customer:
Opt-in
Through the action of Opt-In, the user requests at some point during registration, whether on the website or with the company, agreeing to receive communications via email. This is the most correct way to start an email marketing relationship strategy, with the proper entry of this user into your relationship list.
The Opt-in can also occur through other means, such as the user's entry through other contact points with the company, like Social Media, Search Marketing, or even participating in some cultural contest.
Opt-Out
This is the act of unsubscribing, through which the user informs the sender that they no longer wish to receive that communication via email and that they want to be removed from the email list.