You can set up a specific opt-out link for each connected email account. Go to the Settings > Email Accounts, hover the mouse on the certain email account and the wheel settings will appear. Click on it and scroll down to the “Opt-Out” section. 

Enable the “Use Opt-Out” and write the opt-out sentence in the box below. 

To convert the specific part of the text to a link – use {curly brackets}. Example: “If you don’t want to receive my emails anymore, {unsubscribe here}”. In this case, the text “unsubscribe here” will be a link, and the other remaining text will stay without links. Click “Save” when it’s done.