Unsubscribing to the mail list is a fairly straightforward process. At the top of every single XR Mailing list email there is a link to enable users to removed themselves from the mailing list. This page has been added as there has been confustion over this issue in the past. Simply send an email from the email address you subscribed to the list with, to the unsubscribe email address mentioned below, and on the emails.
Sometimes it seems after unsubscribing that people continue to receive emails for a short time. This shouldn't continue for too long after unsubscribing.
If the mail based unsubscribe process does not work for you then email contact_justxr.com and ask to be manually removed from the list.