Log in to SmarterMail as admin.
Click on the Settings icon at the top of the page.
Click on Domain Defaults in the left window pane.
Click on the Limits tab.
Set the Disk Space Quota setting in the first box.
Note: This setting only affects future domains created, and will have no bearing on existing domains. To effect this change on all existing dmains, take the following steps:
Click Domain Propagation on the left side.
Click the Limits tab.
Check the box next to Disk Space.
Click Propagate Now.