Viewing email disk usage through SmarterMail

Email disk usage may be reviewed from the SmarterMail web interface.  When logged in as Primary Admin, by default, both the total usage as well as a breakdown by email user is available.  To log in automatically as the Primary Admin from the Winhost Control Panel, click Sites > the applicable domain name > Email > then the "SmarterMail Manager" link.  Note that the total disk space available is dependent on plan type:
Primary Admin
To view mail usage for the entire domain, click Domain Reports1 (bar graph with small globe) then Overview2.  The Disk Usage pane3 will list all email users, their individual disk usage totals, and the sum of those totals out of the total email disk space available for the account.  If the left menu is not expanded, click the hamburger4 icon in the upper left corner of the screen.
To view a disk usage breakdown by email folder for an individual user, click the Disk Usage link then the applicable email user.  Note that the "Disk Space Limit" listed here is the allotment for that specific user.  Adjusted at Domain Settings > Accounts > click on the applicable user > "Mailbox Size Limit" field.  After clicking one of the listed email users, the Disk Usage pane will update with the disk space breakdown by email folder.
Email User
Click Reports1 (bar graph) as the Primary Admin or as another email user and the Overview2 will display the disk space being used out of the total allotted by the Primary Admin.  Clicking Disk Usage3 will update the pane with a breakdown by email folder.