The list-unsubscribe email header has been around for quite some time. Hotmail, Yahoo, Gmail, and many others have adopted this to assist with unsubscribing from mailings.
When the header is found in the message source there will often be an “Unsubscribe” button in the email client to unsubscribe from that mailing list. This makes it easier to unsubscribe and less likely that the subscriber will flag it as spam (rather than searching for your unsubscribe link)
The header will often look like:
List-Unsubscribe: <mailto:firstname.lastname@example.org>, <http://domain.com/unsubscribe.php?id=123>
Including this has a number of direct advantages such as:
- Making it easy for subscribers to unsubscribe – Thus less complaints
- Fewer people needing to mark it as spam (many people will do this if they do not want to search for your unsubscribe link)
- Increased deliverability – including the header is often thought as a positive thing from most filters and ISPs
If you are using 1-2-All 5.0 your mailings will automatically add this header for you whenever you have an unsubscription link anywhere in your mailing.
If you are still using an older version of 1-2-All (such as 4.8x) you can add this header by going to Lists > Custom Headers