I've looked over a few posts on multi threading with the OOM and I understand
that the OOM itself is restricted to being single threaded. I could use some
information on how this works.

What I currently have is a MailItem object being passed to a new background
thread every time an event occurs (Explorer.SelectionChange for example). In
the thread I access things like SenderEmailAddress, ReplyRecipients. Is this
thread safe?

What happens if I access a OOM object from the worker thread that wasn't
explicitly passed to it (Example: changing the visibility of a button on a
ribbon bar). I'm guessing this isn't thread safe.

Is there any way to trigger an event on the main thread once the worker
thread has finished running? I am used to doing this with forms, and having a
worker thread invoke a delegate on the main form. Since we're not working
with forms, or even controls for that matter, how would I go about doing this?