Outlook can show the size of a mailbox and each folder, but only if the folder size information is available from the data file or server. The supported way to see it is:
- In Mail view, select the mailbox or folder.
- Select Folder on the ribbon.
- Select Folder Properties.
- Select Folder Size.
The dialog then shows the size of the mailbox and each subfolder in kilobytes.
If the dialog shows an error instead of sizes, the folder size information is not being returned correctly from the server or data file. In that case, use the mailbox normally and try again later, or reduce mailbox contents (for example by archiving or moving items) using the folder list rather than relying on the size dialog.
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