G'day Shaun. That bit only works when an Email is sent in and LANDesk LDSD doesn't recognise the address as belonging to anyone. If no email is sent in, no user gets created. So you could ask them all to mail in or if you have a list in some other format they could be imported easily enough. I've also set up a system before which allows people to fill in a registration page which then causes a processes to be fire off, gets authority from the SD manager and then automatically creates the contact. Some food for thought anyway.
Alternatively if I use the create a user for unknown users is there away to associate automatically these unknown users with a Company and Group automatically if they were all to be joined to the same one. For example the users that are on the domain already imported by schedule are associated to our company group and department groups but the new unknown users I want to join them automatically to another company group and department group, how could this be handled if at all possible.
I think you'd need a DB scripted solution for that. Something along the lines of take all the end users that have been given the role created by the incomming email and do not have a current customer or company group and pop these into a given company group and customer group.
Depending on who did your implementation, you might find they could supply you with scripts to do this as I guess they must have done the other scripts that associate your domain users in a similar way. If that isn't possible, you might want to contact your local support team as ask if they have one to hand. It will need to be tailored for your environment.