Thunderbird: moving email from local Junk folder to IMAP folder yields "Message contains invalid header"

Thunderbird: moving email from local Junk folder to IMAP folder yields "Message contains invalid header" Whenever I try to move an email from a local Junk folder to an IMAP folder in Thunderbird, I get the following error message:
Asked by: Guest \| Views: 286

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Guest [Entry]

"Found this article : ""Fix invalid mail headers when moving from Thunderbird to IMAP"", where a Python script is proposed that fixes all mailbox files in a given directory.

Even if you don't use Python, it should be quite easy to do the same in another language or a text-editor or sed. Apparently, this fixed the problem for the author of the article."