Event ID - 238

Event Id238
SourceMSExchangeDSImp
DescriptionThe e-mail address specified for import object Useralias is not unique. MBX:1 has already been assigned to Address Book entry /o=<Organisation></ou=Site></cn=container></cn=<useralias>>
Event InformationAccording to Microsoft:
CAUSE:
The import procedure does not work because you cannot use the same proxy address, of any type, for more than one recipient. In this case, the value of MBX:1 or MBX:0 is assigned to the first record in the .csv file and cannot be assigned to any subsequent entries in the .csv file.
When you use the Mailbox Manager tool, you can either include or set a policy for each container to exclude a mailbox. Corresponding to the selection, the tool generates a proxy address for the corresponding mailbox of either type MBX:0 or type MBX:1. However, if you try to import a .csv file, it does not work and you receive the error message that is mentioned in the "Symptoms" section.
You can use Mailbox Manager to select mailboxes that you want to exclude from automated message deletion. With MBClean, there was a limit to the number of mailboxes that could be excluded. This limitation was caused by the way that the mailbox exclusion information was being stored. To overcome this limitation, Mailbox Manager stores the exclusion information on the mailbox itself. Mailbox Manager uses a custom proxy address of type MBX and adds this proxy address to each mailbox that is excluded. For example, if you use Mailbox Manager to exclude a mailbox named "Test," a proxy address of type MBX is added to the Test mailbox. When Mailbox Manager processes the mailboxes for cleanup, it ignores the mailboxes that have the proxy address MBX.
Reference LinksError when you import a folder with MBX proxy addresses

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