I would like to export a list of email addresses of people I have previously sent mail to. I don't think there is a way to do this without an add-in.

I tried a tool called Gwabbit and it did not do what I needed.

There are some answers here based on the NK2 file and utilities that read it, but it's not the solution because the NK2 file will not always have every recipient you've ever emailed for the following reasons:

1. You can edit it (simply by deleting a suggested contact as it pops up)
2. It's unique to your profile (each login on each device, not counting roaming profiles), so if you use multiple machines/devices it doesn't get all recipients.

What I really want is to go through all the sent mail, optionally my received mail too, and harvest all the email addresses in there.

I initially wrote this question for Outlook, but if there is an app or utility that will do this outside of Outlook, it's worth migrating mail, even if just for this one time need.