Through code it's possible 

Create a custom specific entry point for AWRKMEL

Write some code similar to below to set the EXP_EMAIL variable.

(I even created a field on the workflow screen where the user can specify an email address. If there is a value there then I use that email for the sender if not I don;t do anything and the user;s email is used.)

$ACTION

Case ACTION
When "EMAIL" : Gosub EMAIL
Endcase
Return

$EMAIL

 EXP_MAIL = "[email protected]"

Return

Can this be set up in a way that it will only use the specified email when specific workflows are ran?

Hi jtansey I have written a customization where I added a custom field on the Workflow called "Sender" and a Custom checkbox that that executes only when the checkbox is checked.

Yes it can as I wrote in the parenthesis, I created a field on the workflow where I can specify the sender email's address for that workflow and if it's blank then the system uses the user's email.  

Is this working with the notification server, instead of the traditional smtp send server?