User has to send email to a restricted "All Users" group using a shared mailbox he/she has "Send On Behalf" permissions.
If user's own account is permitted to send emails to "All Users" group this thing works fine for "Send On Behalf" mailbox as well.
This is the real trouble, some users forget to change the "From" field and end up sending email to "All Users" group from their own mailbox and this creates a lot of inconvenience.
Is there a way to restrict users so that they can only send email to "All Users" group if "From" field is set to shared mailbox not their individual one?