Commercial email messages are governed by CAN-SPAM law that organizations are obligated to adhere to for their email marketing programming. The algorithms that are in place at ISPs determining your sender score are looking at several different things, and having an opt-out link is an essential item they look for in your email. Not including an opt-out link can impact your sender score. Marketing Emails sent without an option to unsubscribe can decrease your deliverability to inboxes.
Sending Marketing emails without is not best practice and does not follow the CAN-SPAM, Canada’s CASL, and GDRP requirements.