Google has specific markup to make it easier for them to collect your data (and provide some UI niceties for GMail users). https://developers.google.com/gmail/

Google has specific markup to make it easier for them to collect your data (and provide some UI niceties for GMail users). https://developers.google.com/gmail/markup/reference https://developers.google.com/gmail/markup/reference Not just any email sender is allowed to use them though.