UnicodeEncodeError: 'ascii' codec can't encode character

[CipherGuardianSweden]

[config.yaml] 2022-04-19 23:39:12:ERROR:Exception raised during forward()
Traceback (most recent call last):
  File "imap2imap.py", line 85, in run
    dest_imap_config=self.config['dest_imap']
  File "imap2imap.py", line 184, in forward
    mailbox=dest_imap_config.get("mailbox", "INBOX")
  File "imap2imap.py", line 354, in upload_message
    message=msg.as_bytes()
  File "C:\Python34\lib\email\message.py", line 178, in as_bytes
    g.flatten(self, unixfrom=unixfrom)
  File "C:\Python34\lib\email\generator.py", line 116, in flatten
    self._write(msg)
  File "C:\Python34\lib\email\generator.py", line 181, in _write
    self._dispatch(msg)
  File "C:\Python34\lib\email\generator.py", line 214, in _dispatch
    meth(msg)
  File "C:\Python34\lib\email\generator.py", line 264, in _handle_multipart
    self.write(subparts)
  File "C:\Python34\lib\email\generator.py", line 406, in write
    self._fp.write(s.encode('ascii', 'surrogateescape'))
UnicodeEncodeError: 'ascii' codec can't encode character '\xf6' in position 26: ordinal not in range(128)

I got also the same mail over and over on the host side. Any solution to this? Otherwise a good script.