We know. Breaking up is hard to do. You put a lot of effort into gaining every subscriber to your list. But when push comes to shove, your subscribers need to have the final say in whether they stay subscribed to your mailings or not. Unsubscribes do NOT negatively affect your mailing reputation but clicks on the SPAM button do. That’s what subscribers do when they can’t easily find a way to unsubscribe from your mailings.Fortunately, the Internet Wizards figured out a way to let subscribers easily unsubscribe from any email subscription so they respond with a spam complaint which lowers your sender reputation. It’s called the List-Unsubscribe X-Header and most major ESPs give you the ability to automatically add it to all of your email campaigns.The List-Unsubscribe X-Header was originally created by RFC 2369 [Link to: https://www.ietf.org/rfc/rfc2369.txt]  back in 1998.   The standard allowed for a hidden email header field in the format of either a Web-URL or a Mailto: email address or both. Using both was recommended since different email clients and providers used one or the other.  The List-Unsubscribe header would look like this in the hidden email header block:List-Unsubscribe: <http://www.acme.com/list.cgi?cmd=unsub>
        <mailto:list-request@acme.com?subject=unsubscribe>This is what your Gmail recipient sees when you have List-Unsubscribe correctly enabled:

Once the recipient clicks the ‘Unsubscribe’ link they will see this confirmation:

Recently the standard has been upgraded to resolve an issue with the unsubscribe URL link method.  Anti-spam software frequently checks every link in an email message for malicious content. This resulted in a lot of accidental unsubscribes.  The new standard outlined in RFC 8058 [link to https://tools.ietf.org/html/rfc8058 ] adds another line that prevents accidental unsubscribes by anti-spam software while retaining the hands-off one click unsubscribe functionality.  It looks like this:List-Unsubscribe: <mailto:list-request@acme.com?subject=unsubscribe>                                     <http://www.acme.com/unsubscribe.html?opaque=987654321>                             List-Unsubscribe-Post: List-Unsubscribe=One-Click Now if the link is manually followed in a browser or by anti-spam software, a landing page will be displayed that does not result in an immediate unsubscribe but would offer an unsub button instead. The email client will perform a POST request on this URI and sending the key/pair value from this header will create the unsubscribe without any user interaction.The most popular email clients all support the Mailto Method and support for the RFC 8058 is gaining ground. Here’s a chart showing which email client supports which method.

Using List-Unsubscribe headers on all your email campaigns is the recommended best practice and contributes to improving your sender reputation and improves the user experience for your subscribers.You can keep track of your List-Unsubscribe performance with Inbox Tracker’s Reputation Advisor. If Reputation Advisor fails to find a List-Unsubscribe header in your emails it will display in the Policy & Practices section of the Reputation Advisor Dashboard.

So give your subscribers an easy and convenient option to unsubscribe from email they don’t want and ultimately you will improve your delivery rates by reducing complaints and keeping your subscribers happy.