To overcome email being classified as spam by Gmail, Google recommends a number of steps, which we have implemented (namely SPF, DKIM, and Precedence: bulk).One additional measure they recommend at https://support.google.com/mail/bin/answer.py?hl=en&answer=81126#authentication reads as follows:Because Gmail can help users automatically unsubscribe from your email, we strongly recommend the following:Provide a 'List-Unsubscribe' header which points to an email address where the user can unsubscribe easily from future mailings (Note: This is not a substitute method for unsubscribing).Documentation for List-Unsubscribe is found at http://www.list-unsubscribe.com/. From this documentation I expect a button to be provided by a supported mail client.I have tested the 'List-Unsubscribe' header and it does not appear to provide the button. I have tested in both Gmail and OS X Mail. I tested with an http address and with both an email address and an http address. The format of the header is as follows:List-Unsubscribe: <mailto:unsubscribe-espc-tech-12345N@domain.com>,  <http://domain.com/member/unsubscribe/?listname=espc-tech@domain.com?id=12345N>No button appears in any test.My questions:How widely is List-Unsubscribe supported?Should a button be appearing somewhere, or does something else have to be present?I have seen a comment that even if the button is not present, services like Gmail, Yahoo, Hotmail/Windows Live would give higher regard to email having the header. Thus it might be worthwhile for this aspect alone.Please note that our standard email footer already contacts instructions and a link to allow unsubscribing from our email.Finally, is it worth while to implement this header? (That is, any downsides?)
Use of list-unsubscribe to improve inbox delivery
email;spam;gmail