Recently i could not add MySQL user to MySQL Database in cPanel. There was no error message displayed on screen. The operation just failed.
Then i tried to use cPanel MySQL Database Wizard to create a new database, new user, and add that new user to the new database. Then i saw the error message in my browser.
There are various reasons why CSF firewall may make your WHM / server slow.
Here are some personal tips from me.
Here is what i did to install PhantomJS in cPanel / WHM 🙂
DKIM is one of useful thing to make email which is sent by your domain to be avoided marked as spam.
When you use cloudflare for that domain, there is some change that you need to do on the DKIM key.
For example on your WHM (Edit DNS Zone) or cPanel (Email > Authentication), you will get DKIM key with format like this :
"v=DKIM1; k=rsa; p=XXXX" YYY\;