App to upload or edit IMAP messages

Question

Is there a modern Windows software like IMAPSize, an open source (formerly freeware) program, that can modify or at least upload IMAP messages? While IMAPSize still works, being abandonedware it carries noticeable issues, like:

1. It can't edit messages, only upload new ones. I can live with that, but:
2. It doesn't care which date stamps the messages have, instead opting to upload them as new. I.e. doesn't have support for sending the parameter which PHP describes as internal_date.
3. It only supports username/password and not OAuth, which is both insecure and blocked by default in places like Gmail.

A webapp service is acceptable too.

Answer 1

A similar question was asked at the wrong forum almost a decade ago. I probably didn't find it before because it asks about MBOX and not EML, but they're not too different from each other.

Be it as it may, one of the answers there actually survived time and even supports OAuth - the free and open source Got Your Back (GYB). Beware it's Command Line though and a bit advanced to install. To solve the issue of OAuth, it basically makes you register your own program at Google Cloud and uses it for OAuth. And if your Google account is free, Google forces "your app" to be public (you can only bypass it by leaving "your app" in test mode while adding your own address to users "who are allowed to test it"). Finally, you'll need to rename your EML files to MBOX in order to use the "restore MBOX" option. (Update: fixed)

With that said, the usually freeware Pop Peeper supports IMAP Uploads but only if you buy the Pro license.