Allow registrations only from specific domain?

I am very new to Vanilla forums, moderately familiar and comfortable with php. I am creating a forum that is specifically only for our company, which is currently approximately 100 users. Obviously, I do not want to set them all up. However, while I intend on keeping the bots out and hopefully off search engines (as much as possible), I would like them to be able to register themselves and anyone new coming on board in the future. That being said, I would also like to not have to go through registration approval if possible so I think something custom is in order here, just not familiar enough to figure out where to start.
I want the registration process to be automated; HOWEVER, I want to restrict registrations to only our company domain email addresses. i.e. No one can register unless they have mycomany.com email address.
Well, surely anyone can put that in, but I can restrict any spammers because they will not actually get the confirmation email.
Thanks!