When deploying Workflow Outbound Messages, if you receive an error "User Does Not Exist in Target" follow these steps:
Handling "User Does Not Exist in Target" Error:
Go to the Salesforce (SFDC) target environment where you are deploying to.
Locate the username of the user mentioned in the error.
Edit the NACL in your deployment to include exactly that username.
Save and apply changes.
Once the NACL is updated, the error should disappear from the deployment. It should now complete successfully.
By ensuring that the NACL contains the correct username, the deployment process will be able to recognize the user and proceed without issues.