Hi,
According to my research, I find an solution for your question. For your reference:
https://social.msdn.microsoft.com/Forums/office/en-US/e2db1734-d526-4f59-bde5-6697c574894c/email-after-pst-import-done-via-powershell
$Data = New-MailboxImportRequest -Mailbox "Test" -Archive -FilePath "\\test\test\test.pst"
Set-Notification -NotificationEmail @('Test@Contoso.com') -Identity $Data.RequestGuid.ToString()
Thanks