Is it possible to create a token in hook_civicrm_tokenValues that retrieves the name of the creator of a non-mass-mailing?
For the use case where the email is sent from a logged in user, one could use the function CRM_Core_Session::singleton()-&gt;getLoggedInContactID() to get the logged in contact ID.
This would fall down for those cases where the email is generated by a 'system call', e.g. an email that was triggered by a cron job, but that might not be a deal breaker for your use case..
You could always add a fallback behaviour for those situations where it has not been possible to find a contact by either your method or the above method, e.g. populate the token with 'your friendly membership officer' or provide a default contact id or similar.