Protecting your sender reputation is essential to maximizing your email deliverability. Many inbox providers, e.g. Yahoo, Gmail, Hotmail / Outlook.com, or AOL, opt to limit or refuse message traffic based on it. Continuing to send messages to invalid email addresses or to recipients who no longer want to receive your emails can negatively impact your sender reputation. By maintaining an up-to-date suppression list, you can avoid sending unwanted messages. A suppression list — or exclusion list, as it is sometimes called — is a list of recipient email addresses to which you do NOT want to send email.