def add_webhook_identifier_to_email(email)
			email.message.mailgun_variables = {}
        	email.message.mailgun_variables["webhook_identifier"] = BSON::ObjectId.new.to_s
        	email
		end
def add_webhook_identifier_to_email(email)
			email.message.mailgun_variables = {}
        	email.message.mailgun_variables["webhook_identifier"] = BSON::ObjectId.new.to_s
        	email
		end
returns the email after adding a webhook identifier variable.