new-databaseavailabilitygroup -name dag01 -WitnessServer  msp-dag01.contoso.local
Add-DatabaseAvailabilityGroupServer -Identity dag01 -MailboxServer msp-exc01
Add-DatabaseAvailabilityGroupServer -Identity dag01 -MailboxServer msp-exc02
add-MailboxDatabaseCopy -Identity db01 -MailboxServer msp-exc02
add-MailboxDatabaseCopy -Identity db02 -MailboxServer msp-exc01