how does the migrationbatch decide on mailbox allocation?
new-migrationbatch -local -name blah -csvdata ([System.IO.File]::ReadAllBytes("c:\dump\blah.csv")) -Targetdatabases db1,db2, db3 -autostart -notificationemailsme@msn.com -autoretrycount 2
also is it necessary to remove-migrationbatch ?