From: Sender <sender@pm.me>
To: Receiver <receiver@pm.me>
Content-Type: multipart/mixed; boundary=longrandomstring

--longrandomstring

body
--longrandomstring
Content-Type: application/octet-stream
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename*=utf-8'%F0%9F%98%81%F0%9F%98%82.txt

aWYgeW91IGFyZSByZWFkaW5nIHRoaXMsIGhpIQ==
--longrandomstring--
