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Cannot access user mailbox using Outlook

In Exchange 2010 SP2 environment, trying to export mailbox to PST using command New-MailboxExportRequest which failed with the following:

VERBOSE: [14:29:34.478 GMT] New-MailboxExportRequest : Processing object “RequestGuid (5b9bbd13-eff0-491a-8d2b-a3bbf9224157), RequestQueue: (2b83b505-9dad-4f09-b2da-4c5759894e31)”. VERBOSE: [14:29:34.634 GMT] New-MailboxExportRequest : Couldn’t connect to the source mailbox. –> MapiExceptionUnknownUser: Unable to make connection to the server. (hr=0x80004005, ec=1003) Diagnostic context:     Lid: 59431   EMSMDB.EcDoConnectEx called [length=106]     Lid: 34855   EMSMDB.EcDoConnectEx returned [ec=0x3EB][length=56][latency=15]     Lid: 59505   StoreEc: 0x3EB     Lid: 52465   StoreEc: 0x3EB     Lid: 60065     Lid: 33777   StoreEc: 0x3EB     Lid: 59805     Lid: 52209   StoreEc: 0x3EB     Lid: 56583     Lid: 52487   StoreEc: 0x3EB     Lid: 19778     Lid: 27970   StoreEc: 0x3EB     Lid: 17730     Lid: 25922   StoreEc: 0x3EB VERBOSE: [14:29:34.649 GMT] New-MailboxExportRequest : Admin Audit Log: Entered Handler:OnComplete. Couldn’t connect to the source mailbox.     + CategoryInfo          : NotSpecified: (0:Int32) [New-MailboxExportRequest], RemotePermanentException     + FullyQualifiedErrorId : E8CB8120,Microsoft.Exchange.Management.RecipientTasks.NewMailboxExportRequest VERBOSE: [14:29:34.649 GMT] New-MailboxExportRequest : Ending processing &

So tried to access mailbox using Outlook, but it errors stating ‘Server cannot be found’. I can access mailbox from OWA (open another mailbox option) but when try to open mailbox as an additional mailbox in Outlook it fails.

Checked for Mapi protocol and found it to be enabled in mailbox features. Tried moving mailbox to another database, disconnected mailbox from original AD account, created new user account and reconnected to new user account to check for AD permission issue, still can’t access mailbox.


Try to run New-MailboxExportRequest command for other users and if it works then the issue might be to a particular user mailbox. Please run following command to verify the issues related to problematic mailbox:


Get-Mailbox user1 | FL

Get-MailboxStatistics user1 | FL


Also check for AD Users and Computers and verify the attribute values for: LegacyExchangeDN and HomeMDB. LegacyExchangeDN value for any Exchange recipients (mailbox, resource mailbox, linked mailbox, contact, groups etc.) should be unique across AD forest.

While SMTP addressing is the de facto e-mail addressing standard, Exchange internally still uses an X.500 addressing scheme. Using X.500 implies that an X.500 is required, which is why mail objects in an Exchange organization such as mailboxes, require a properly populated legacyExchangeDN.

Clients like Outlook cache information like the legacyExchangeDN for name lookups.

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