BTW: I removed the whole maildir contents and restarted the downlowd over night. here's the result:

---------------------------------------------------------------
Traceback (most recent call last):2|####################                                                          | 26% ETA:  1:37:22   3.11  emails/s
  File "./gmail-notmuch.py", line 253, in <module>
    main()
  File "./gmail-notmuch.py", line 89, in main
    download_new_messages(imap, database, new_messages, destination)
  File "./gmail-notmuch.py", line 210, in download_new_messages
    tag_message(database, dest, labels)
  File "./gmail-notmuch.py", line 168, in tag_message
    raise e
notmuch.errors.FileNotEmailError
-----------------------------------------------------------------------

/p