You receive the following error when trying to import a pst file with a large message to an Exchange mailbox.

Error: This mailbox exceeded the maximum number of large items that were specified for this request.
Solution: Raise the -LargeItemLimit size above the default 35mb.

Example:
New-MailboxImportRequest -Mailbox Ben -LargeItemLimit 50 -AcceptLargeDataLoss -FilePath serverben.pst