Give user Send As permission

Commands

View Send As permission for a specific user

PS C:\Users\Administrator> Get-RecipientPermission -Trustee user1

View Send As permission for a group

PS C:\Users\Administrator> Get-RecipientPermission group1

Give a user Send As permission

PS C:\Users\Administrator> Add-RecipientPermission group1 -AccessRights sendas -Trustee user1 -Confirm:$false

Give a user Full Access to a mailbox

PS C:\Users\Administrator> Add-MailboxPermission user2 -User user1 -AccessRights FullAccess

Revoke Send As permission

PS C:\Users\Administrator> Remove-RecipientPermission group1 -AccessRights SendAs -Trustee user1 -Confirm:$false

Source : https://technet.microsoft.com/