Handling outlook checkbox when sending email with python

My company has an outlook add-in that pops up a checkbox when sending email to an external source. I have a python program that needs to send an email to the same external email address every time. So looking for a way in my code to automatically check the box and click the send button.

import win32com.client as win32

outlook = win32.dispatch('outlook.application')
mail = outlook.CreateItem(0)
mail.to = 'external email address here'
mail.subject = 'update'
mail.body = 'body of the message'
mail.Send()