Hi,
Based on my experience, it is not feasible to achieve this requirement with build-in features.
I tried to set up a rule to delete these emails in user’s sent items, in Outlook click File->Rules and Alerts->New Rules->Select a template__:Apply rule on message I send__->Select conditions :through the specified account ->Select Action__:move a copy to the specified folder__ and selet Deleted Items
But this fails, the rule can only copy from sent items to deleted items, it doesn't delete them.
Hope this helps!