Prevent users from sending an email attachment in sql server

In SQL Server, I want to restrict all users (except a few specific users) to send an email with attachment. For example, someone import data into excel file and send it via mail using the sp_send_dbmail procedure. Can we restrict use of this procedure? Or is there any other way to do it? There are some users that have sysadmin permission, I want to restrict them too. If it is not possible, at least I want to get notification when someone sends an email with attachment. Trigger or procedure might work, but I could not get any result.