As mentioned by Chi Chen, in first step,you will need to create a new notification method for each of your tenant ehere you can overwrite the from address using the -F and -T tags like below as an example:
pdm_mail -F "myemail@ mytenant.com" -T "myemail@ mytenant.com"
the in step 2 you will need to update each contacts of the corresponding tenant to use this new method.
Hope this help.
/J