I want to Increase the number of mail ID allocation for my Domain

If you want to change the number of Email IDs for the domains which are created under your WHM ( reseller account),

1. Login to the WHM by using servername/whm
2. Create a new package according to the specification.
3. Click on Upgrade/Downgrade an account option under Account functions.
4. Select the domain name and click on Modify.
5. Select the new package and click on Upgrade/Downgrade.