Receive-As permission needs to be applied with the add-MailboxPermission
Send-As permission needs to be applied with the add-ADPermission
Mailbox level:
Use the Add-MailboxPermission cmdlet to add permissions to a mailbox
AD level:
Use the Add-ADPermission cmdlet to add permissions to an Active Directory object
For Add-MailboxPermission, see:
https://technet.microsoft.com/en-us/library/bb124097(v=exchg.160).aspx
For Add-ADPermission, see:
https://technet.microsoft.com/en-us/library/bb124403(v=exchg.160).aspx