[https://infosec.rm-it.de/2017/08/07/sha2017-ctf-network-300-abuse-mail-challenge/](https://infosec.rm-it.de/2017/08/07/sha2017-ctf-network-300-abuse-mail-challenge/)

Original writeup (https://infosec.rm-it.de/2017/08/07/sha2017-ctf-network-300-abuse-mail-challenge/).