Having used Outlook for years and years, there is one feature I've always wished was there, though it has never been a show stopper, just a nice to have. A Bounce feature that would take an email meant for someone else and send it on to them as if it was originally sent to them. I know, nothing that couldn't be simulated with a forward. I've also seen some 3rd party utils out there that have functionality like that (as well as some other email clients)....I've just always been curious why Outlook has never offered that feature. Even just a button in the toolbar to bounce the current email would be fine with me.
At a former employer, one of my last tasks for them was to write an email client that integrated with their other custom software (they didn't want to integrate their software with Outlook, but wanted to write their own package to distribute to their clients). The functionality rivaled Outlook (it was when Outlook 98 was the current version).
One of the extra's I added was a bounce button. It was one of the favorite features for them and came in handy for them. The people using the client were often small offices that would have a central email setup (like a sales email) where all emails would come into. The software did implement rules which could filter some out to the correct users, but often it would take a human eye to determine who the email should go to. The bounce feature worked great for the situation as the email appeared to come from the original sender and was easily replied to.
While I don't have a huge need for this feature in Outlook, unless I am missing something, it seems that this might be a nice feature to have for some people.