The past few years have seen an increased effort, not only from governments but also from software vendors, to curb the misuse of bulk email. CAN-SPAM is the most well known, imposing penalties for various infractions, such as not including the ability to unsubscribe.
In addition, email applications such as Gmail, have introduced auto-unsubscribe functionality, where they proactively ask users if they want to unsubscribe from certain promotional emails. This action is primarily triggered by low open rate of email content.
All of this means that your newsletters and promotional emails need to be more engaging and your lists need to be streamlined and segmented to effectively target recipient interests.