If you migrated a mailbox from another Exchange System (2000/2003) mailboxes are sometimes migrated as legacy mailbox.
To fix this issue, user following cmdlet in PowerShell:
Set-Mailbox -Identity mailboxname -ApplyMandatoryProperties
Zitrox GmbH Technology Blog
If you migrated a mailbox from another Exchange System (2000/2003) mailboxes are sometimes migrated as legacy mailbox.
To fix this issue, user following cmdlet in PowerShell:
Set-Mailbox -Identity mailboxname -ApplyMandatoryProperties