Hi,
Jobroller allows job seekers to apply for a job with or without registering to the site.The main difference is that a registered user can also create resumes and then assign them or link them for each job they are interested in.
so for example job seeker 'dimitris' can create two resumes one for a 'developer' position and another for a 'designer' position.When he finds a designer job he can assign resume 'designer' and apply for the job.
Both registered and unregistered job seekers are using the 'apply online' form to apply for the job. The form sends the email with the subject "Application for job 'designer' " so you cannot really set the subject field.
Please let me know if you need more information about the theme.