Compliance: Many jurisdictions have stringent anti-spam laws that mandate opt-in consent, such as the GDPR in the EU and the CAN-SPAM Act in the US. Engagement: Subscribers who have opted in are more likely to engage with your emails, leading to higher open and click-through rates. Reputation: Maintaining a positive sender reputation is essential for email deliverability. Opt-in permission helps reduce complaints and spam reports. Trust: Building a list based on permission fosters trust and enhances your brand's credibility.