The following Exchange Management Shell commands will accomplish this. One useful trick is to grant this permission to itself. Doing so will eliminate any need to manage these permissions in the future, if a user is a member of the Distribution Group then they also are granted the permission to send on behalf of that Group.
Add Send-On-Behalf rights to its own Distribution Group members
- Set-DistributionGroup "Sales Team" -GrantSendOnBehalfTo "Sales Team"
Check the Send-On-Behalf rights set on a given Distribution Group
- Get-DistributionGroup "Sales Team" | fl name,grant*