Hi partner,
Make a process run automatically needs a trigger condition, in your case, the condition is when the email address no longer valid, but how do the system know the address is invalid? And what's the correct address do you need the system to update?
Actually, if you want to monitor which contact's email address has been invalid, we could do this in D365 with OutLook and Flow.
1.When you send an email to an invalid address, Microsoft will response you an email to tell you that the email address is invalid.
So you need to create a new folder in you inbox first and create a rule to make all these type emails move to the folder automatically.
Then all the emails that tell you the address is invalid will be moved to this folder automatically.
2.Go to Dynamics 365 Settings->System Settings, click on "Use folder-level tracking for Exchange folders (server-side synchronization must be enabled)" to allow you track emails in the folder in D365.
And select "Allow messages with unresolved email recipients to be sent" to "Yes" to allow D365 send email to invalid address(otherwise when you send email to invalid address in D365, there will be a JS error on the form).
3.Go to personal settings, configure Folder Tracking rules.
Select the folder in your inbox to track in D365, this will make D365 create a new email record when your outlook receive a new email in your folder.
Ok, now when you send an email to an invalid address from D365, there will be a new email record created in D365 to tell you that this email address is invaild, yes, here is the trigger condition for our process.
Next we need to know which contact address has been invalid .
The email content will contains the invalid address, so we need to split it out with FLOW.
About how to split the email address from email content, you could use "split" function. Please refer to the following links.
https://community.dynamics.com/365/f/dynamics-365-general-forum/386972/rules-to-automatically-create-or-update-records
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/functions/function-split
If my understanding is not correct, please feel free to let me know and provide more details.
Best Regards,
Leo