Remove Completed Import Requests
Get-MailboxImportRequest -Status Completed | Remove-MailboxImportRequest
Remove Failed Import Requests
Get-MailboxImportRequest -Status Failed | Remove-MailboxImportRequest
Remove Completed Export Request
Get-MailboxExportRequest -Status Completed | Remove-MailboxExportRequest
Remove Failed Export Request
Get-MailboxExportRequest -Status Failed | Remove-MailboxExportRequest