Dear Paul,
Good day!
Thank you for posting to Microsoft Community. We are glad to assist.
Based on your description, I understand that you need to auto update tasks created from email conversations.
After thorough research and consults from my end, it’s been concluded this option is not yet feasible. We apologize if we are not able to meet your requirements; however, thank you for bringing this to our attention, we will surely raise you concerns to our Product Team and hopefully this can be included in the future updates.
In the meantime, I did find similar post in the feedback forum Update Tasks from Email Conversations or Link to Email Conversations · Community (microsoft.com). You can upvote or add a comment to push for this if it is in line with your requirement. Otherwise, you can as well raise a new entry in the forum on link Outlook · Community (microsoft.com) such that it can be considered for development by the product team.
I would also like to invite community members and MVPs in the forum to share their knowledge or any workaround and insight on this topic.
Thank you for your kind understanding.
Best Regards,
Ashraf | Microsoft Community Moderator