What does the limiter option do?
The limiter option is used to limit a user from sending mails not more than a preset value in an hourly basis. If he goes beyond the limit, he would end-up getting domain blocked from sending any mail and he would be getting bounce messages for each time he try to send mail afterwards.
How to increase the limit?
The most easy way to do it is from the front end. Below are the steps:
1. Login to the WHM interface.
2. Once on the main page, look to the left hand sidebar and find the Account Functions category and click on the Modify An Account 
3. Select the account you want to work with and click the Modify button at the bottom of the screen.
4. You are now taken to a list of options for the selected account. Scroll down until you see the option named Maximum Hourly Email by Domain Relayed. By default, the Unlimited radio button should be selected. Select the radio button next to the second field and enter the maximum number of emails you wish to allow the domain to send.
5. Now click save at the very bottom.
Now the limiter value has been set!
Now, lets see how we do the same from backend.
1. Login to the server.
2. Using a text editor, open the file
/var/cpanel/users/username
where username represents the account that owns the domain.
3. In this file, edit the line marked in red to the desired value and save.
4. Now run the
/usr/local/cpanel/scripts/updateuserdomains
script. This script constructs the individual threshold files that Exim uses to determine whether the account has reached its maximum email limit.
Now you are all done!
Note:When an account is blocked due to exeeding the max email per hour limit, check in the directory /var/cpanel/email_send_limits . There you will find a file in the name of that account (eg.max_deferfail_indiancafelounge.com ). Remove the file to unblock it.
