I had an unusual request the other day. Dave Smith, a department head, left, and his secretary wanted to keep his mailbox and account active for a period of months while they searched for a replacement. It’s against company policy to keep a terminated employee’s account active, so I offered to export Mr. Smith’s mailbox to a pst file and forward all of his incoming mail to her mailbox. We frequently forward a terminated employee’s mailbox to another mailbox for a month after the last day of employment, so that’s not too big of a deal. We do that by adding a forwarding address to the mailbox. When we delete the former employee’s mailbox after 30 days, the forwarding stops. However, to maintain the forwarding after the mailbox is deleted, I needed to add Mr. Smith’s email address and LegacyExchangeDN to the secretary’s mailbox.

The sequence of events:

1. I queued the mailbox export using New-MailboxExportRequest and verified that it was running.
2. I took a screenshot of Mr. Smith’s e-mail addresses in Exchange and obtained his LegacyExchangeDN by running Get-Mailbox Dave.Smith | Select LegacyExchangeDN.
3. I removed all of Mr. Smith’s email addresses except one that is never used and added them all to the secretary’s mailbox, including the address that corresponded to his user principal name.
4. I then added the LEDN to the secretary’s mailbox as an X500 address.

A while later, I noticed that the mailbox export had failed. I ran the export command again and received this error:

Couldn't connect to the source mailbox.
    + CategoryInfo          : NotSpecified: (0:Int32) [New-MailboxExportRequest], RemotePermanentException
    + FullyQualifiedErrorId : 296E3B9E,Microsoft.Exchange.Management.RecipientTasks.NewMailboxExportRequest

The mailbox was there and the account was there, so I wondered if the failure might be caused by either 1) a conflict between the X500 address on the secretary’s mailbox and the LegacyExchangeDN on Mr. Smith’s mailbox or 2) Mr. Smith’s UPN listed as an email address on the secretary’s mailbox.

I removed both of those addresses from the secretary and added the UPN as an alias on Mr. Smith’s mailbox, then re-ran the export. Viola! The export worked.

Now I can add those two addresses back to the secretary’s mailbox and delete Mr. Smith’s mailbox.