Eudora??? Eudora!!!
Hello, Eudora, I remember using you maybe twenty years ago!!!
Those are "comments" in addresses (yep, a third component, in addition to name and address, not seen much these days).
And it's "Q-encoding", which should have been decoded, but obviously wasn't.
Can you do this:
- Open the message -> Menu -> View -> Message headers
- Copy
- Send as a plain text message
Or grab the "original message source" in Gmail / web (under the drop-down menu next to the reply icon) -> save to a plain text file -> send as an attachment.
Once I have the message or its headers, should not be difficult to fix.