What is Opt-In Email?
The purpose of opt-in emails is to receive permission from your prospects to send them messages. Since there is permission, an opt-in email list is more effective because recipients are more likely to engage with your emails. In addition, they will not report you for spamming, unlike recipients who did not give their permission to receive emails.
It is also worth noting that the current data collection laws are strict and regularly changing, meaning that the lack of compliance with the legislation might tarnish your reputation and get you in trouble with the authorities.