We can set or limit the maximum number of email that can be sent out from the server. It helps in many way and also a security measure if you manage a shared server. The changes can be made for all the domains (accounts) hosted in the server or you can set the number of mails per hour for a specific account also. The steps for achieving it are pasted below.
NOTE: This changes it for ALL domains on the server
1) Login to the WHM for the server.
2) Click on Tweak Settings under Server Configuration.
3) Change “The maximum each domain can send out per hour (0 is unlimited)” under the mail category to the correct setting.
4) Click on “Save” at the bottom of the page.
For individual accounts:
You can follow the path shown below to apply the settings for a particular account:
Home >> Packages features to add and edit packages or Home >> Account Functions >> Modify an Account feature to edit this setting for individual cPanel accounts.