I was worried the server was hacked, I was logged in already as root but couldn't login to CPanel or a new SSHsession. I even reset the password from the shell and it did not work still.
The reason is CPanel Hulk, it detected a brute-force attack so it locked down the root account entirely even from the correct password. According to cPanel the best way around this is to whitelist your IP.........
I experienced this with CPanel's Exim after an auto-update (a Google of this error produces lots of complaints with few clear solutions). In this case I'll put the solution at the top.
Run /scripts/buildeximconf to rebuild the Exim config and it should be fine after that.
mail -vs "from test" firstname.lastname@example.org < .bash_history
cwd=/root 4 args: send-mail -i -v email@example.com