📌Note: If you don't have the permissions to do this, you need to speak with your admin user.
Temporary workaround
You can restore the employee, change their email address and then archive them again by following the steps below:
Find the employee using the organisation search then click into it.
Click Admin then click Un-terminate.
Click Employment then click Position.
Where you see the Work Contact tab, click Edit.
Update the work email address then click Save.
Terminate the employment again.
Permission based
If you have the Termination Editor permission, you can edit the work email directly on the terminated record.
Also worth noting:
After termination, system emails go to the personal email, not the work one.
So, if it’s just for communication, updating the personal email is often the simpler route.