1. Go to the Mail Manager section of the hosting Control Panel.
  2. Click on the numbers under Quota or Messages columns next to your mailbox.
  3. You can customize the following settings. 
    Quota: Enter the maximum disk space in megabytes (MB)
    Max messages: Set the maximum number of stored messages.
    Send e-mail notification at: Choose the usage percentage that will trigger a warning email when the email account is nearing its limits
  4. Click Save.

Note that besides this custom notification, our system will always send a notification at 99% usage reached - this "99% usage" notification cannot be stopped/adjusted.