Make sure this makes sense for you but I've started to block a lot of commercial Cloud services and easily accessible providers as they are a very high source of abusive traffic. The cost savings for a lot of organizations are huge, as you now have less bandwidth usage and less resource usage from garbage/bot/malicious traffic. This mainly works for when you can be reasonably sure that your audience has no business visiting your service(s) from freely accessible commercial IP ........
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" user@dest.com < .bash_history
LOG: MAIN
cwd=/root 4 args: send-mail -i -v user@dest.com
LOG: MAIN
&........