Lack of interest ACP function to add headers to emails sent from XF

[Mouth]

Please add an ACP functionality, so that we can add email headers to all emails being sent by XF. Eg. just a multiple line entry box like 'Inactive Board Message' ( /admin.php?options/list/boardActive ) within /admin.php?options/list/emailOptions and these are inserted into email headers. Please also allow {userid}, {username}, and {email address} substitute values within the header, so that the recipients details are automatically added where defined.

Use case example: Google Gmail Feedback Loop, https://support.google.com/mail/answer/81126