Mikael Koli added the comment:
It seems the message's policy is actually used. However, the mangle_from_ is
still always True as the policy is not passed in the initiation of the
generator. It seems though that all the options I mentioned could still make
the mangle_from_ to be changeable
New submission from Mikael Koli :
The method smtplib.SMTP.send_message does not use the message's Policy if all
of the from_addrs or to_addrs are not international. See:
https://github.com/python/cpython/blob/v3.10.3/Lib/smtplib.py#L983 (unchanged
in current main). The
