[gerben]

Maybe I don't get it but it sounds to me like it is all there, but maybe not out of the box.
There is a script made by an OF user that i use (sorry forgot his name) called "complete and await reply", i have this in my menu bar and use it a lot, for instance for stuff i order online, or other stuff i am waiting for. I hacked it a little so it states a date at the end and "wacht:" (dutch for wait) in front.

Within mail i send a lot of email via the service menu to OF, but you mean something else i guess?