I am studying the SMTP protocol and follow a course materials to setup a PoC spoofed email by talking with a SMTP server of our department.
This is what I have right now:
shuaiw@shuaicpu1:~$ telnet mail.XXXXXX 25 Trying XXX... Connected to mail.XXX.hk. Escape character is '^]'. 220 XXX ESMTP ; Mon, 4 Nov 2019 16:07:07 +0800 HELO random.org 250 XXX Hello 191host060.mobilenet.XXX [XXX], pleased to meet you MAIL FROM: <email@example.com> 250 2.1.0 <firstname.lastname@example.org>... Sender ok RCPT TO: <XXX@XXX> <---- this is a valid email address 250 2.1.5 <XXX@XXX>... Recipient ok DATA 354 Enter mail, end with "." on a line by itself this is the email body . 550 5.7.1 can't determine Purported Responsible Address
I was expecting to send this message out but however, it returns
can't determine Purported Responsible Address. Could anyone shed some lights on this? Thanks a lot.