In Microsoft Exchange Server 5.5, all public folders were mail-enabled and hidden by default. In Exchange 2000 Server and Exchange Server 2003, folders can be mail-enabled or mail-disabled, depending on whether the Exchange Server organization is in mixed mode or in native mode.
If Exchange Server 2003 is in mixed mode, the Mail Disable is not available when right-click a public folder / All Tasks in Exchange System Manager, only the Mail Enable option is available (even the public folder is already mail enabled).
To access the Mail Disable option, change Exchange Server 2003 to native mode.
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