This script can be used either on Script Field Processor (Use Script Field Processor ) which means it is triggered depending on your Directive Processing Behaviour as set mentioned here https://thepluginpeople.atlassian.net/wiki/spaces/JEMH/pages/227115013/Use+Script+Field+Processor#Enable-Directives.

If required in a specific Project Mapping the Script Rule (/wiki/spaces/JEMH/pages/223739905) Please note however the limitation for the Script Rule is that it is processed only during issue creation. This is because it is a Mapping Rule this means it only applies during creation.

Useful background knowledge

We will making use of directives via the resultMap.put(<directive>, <param) more information on directives here Use Directive Sets. Supported fields for directives here: Supported fields for use with Directives.

Prequisites

Project ID

You will need this Project ID to find the Project Object in the script. This can be found via Project Settings > Details in the URL bar of your browser it will be listed as a query parameter as shown below:

Project Role ID

You can find this via Jira Administration > Security > Project Roles then edit the desired role.

Similarly to Project ID you will find the Project Role ID in the URL bar as a query parameter:

Example Script

//Go through each address in ccAddresses
for(var i = 0;i < ccAddresses.length; i++)
{
    //determine is email address is a jira user.
    var emailAddress = ccAddresses[i].getAddress();
    print("[" + emailAddress + "] detected email address");
    var jiraUser = jemhUtils.getUserByEmail(emailAddress);
    
    if(jiraUser == null)
    {
        print("["+ emailAddress + "] was not an email address related to a Jira User");
    }
    else
    {
        print("processing email and attempting to find related users");
        
        //get current project use your own project id here.
        var project = jemhUtils.getProjectContext(10300).getProjectObject();
        print("["+project.getName()+"] Project Found");
        
        //get required project role use your own project id here.
        var projectRole = projectRoleManager.getProjectRole(10101);
        print("["+projectRole.getName()+"] Project Role Found");
    
        //check if the user is in the role  
        var isInProjectRole = projectRoleManager.isUserInProjectRole(jiraUser, projectRole, project);
        print("Is user in the Project Role"+"["+projectRole.getName()+"] returned ["+isServiceDeskTeamRole+"]");
        
        //user is in the role then add them to watcher
        if(isInProjectRole)
        {
            print("["+ emailAddress + "] will be added to watchers");
            resultMap.put("watchers", jiraUser.getUsername());
        }
        //Any other Jira user is added to request participants 
        else
        {
            print("["+ emailAddress + "] will be added to request participants");
            resultMap.put("Request participants", jiraUser.getUsername());
        }
    }
}

Outcome

The result of this example script is that if a non-jira user is found then it will be logged in the report. However if a
Jira user is found then: