How to View Mail Disk Usage in Plesk
When you want to check how much storage your mailboxes are using. This article explains how to view mail disk usage in Plesk.
The Statistics option in Plesk allows you to view the overall disk space along with the traffic under your hosting package.
You may navigate to this option via the Statistics tab post logging into the Plesk panel or via the View More Statistics under the ‘Resource Usage’ tab on the right-hand side of the Plesk page.

You can also refresh mail usage statistics from Plesk>Mail Addresss>Refresh Usage Stats.

Note: On observing multiple cases of users utilizing excessive server resources than allocated, and in turn hampering the experience of other users on the server, we have placed a limit on the mail disk space for a user on our shared servers.