Symptoms
Every time I tried to change the String Table in the server, it changes it for all the processes and the workflow server as well.
Why can't the "From Address" parameter be different for each process?
Diagnoses
This is by design and when a Process string table is changed from the process all processes using the same Environment String Table will see the change.
Resolution
At this point, that is the only solution. Also, if you are using EWS (SmartActions) you can only have one from address since we only check one Mail box per environment.
I did some research and asked around with my peers about this and this is the it has been working. As a workaround, what you might want to try is to create another Environment Template with the FROM Address set to what you want and use that template when you deploy the package.
Another workaround would be to switch to SMTP and be able to change the FROM field and specify the address at design time. This implies that you will not be able to use Smartactions since this change from EWS to SMTP.