You could always export them in various formats and attach them...

Generally speaking, I'm not going to archive e-mail for later response. If there is an e-mail that comes in that needs a response eventually, I hit it with a follow-up flag in Outlook itself and leave it in my e-mail box.

Which I suppose is an important case for using OneNote. The idea is if you start leaving e-mails in your inbox, pretty soon it is so full that managing with flags and category colors is futile. Too much traffic in your inbox and organization becomes unmanageable. So get the TRASH out, the long term archives into OneNote, and the ones that require ARs or follow-up responses either get an immediate reply, or get flagged so you can easily review your inbox and follow up later.

Make sense?

Once a flagged one is complete, click the flag and it will turn into a check, then decide if you need it archived for long term or if you want to delete it.