Email spoofing

How it was found

There are few email spoofing tool is available free.one them is

http://emkei.cz/

when I tried to send a email from ███████ to my email ,it was successful but when i tried to send the another from ██████ , i did not receive any email.Hence, there might be some configuration missing in your mail servers (i am not much aware of technical details associated with this issue but would love to know how this is happening),Arice can explain this to me much better.

This can be dangerous ,as attacker can send some fake bounty amount to some hacker,then hacker will claim back for the money (a sample mail attached),can lead to reputation loss :)