New submission from Grant Edwards <grant.b.edwa...@gmail.com>:
SMTP.send_message() does from mangling even when the message's policy has that disabled. The problem is in the send_messsage() function shown below: 912 def send_message(self, msg, from_addr=None, to_addrs=None, 913 mail_options=(), rcpt_options=()): 914 """Converts message to a bytestring and passes it to sendmail. ... 963 # Make a local copy so we can delete the bcc headers. 964 msg_copy = copy.copy(msg) ... 977 with io.BytesIO() as bytesmsg: 978 if international: 979 g = email.generator.BytesGenerator( 980 bytesmsg, policy=msg.policy.clone(utf8=True)) 981 mail_options = (*mail_options, 'SMTPUTF8', 'BODY=8BITMIME') 982 else: 983 g = email.generator.BytesGenerator(bytesmsg) 984 g.flatten(msg_copy, linesep='\r\n') 985 flatmsg = bytesmsg.getvalue() If 'international' is True, then the BytesGenerator is passed msg.policy with utf8 added, and from mangling is only done if the message's policy has from mangling enabled. This is correct behavior. If 'international' is False, then the generator always does from mangling regardless of the message'spolicy. From mangling is only used when writing message to mbox format files. When sending a message via SMTP It is wrong to do it when the message's policy says not to. This needs to be fixed by passing the message's policy to BytesGenerator() in the 'else' clause also. I would suggest changing 983 g = email.generator.BytesGenerator(bytesmsg) to 983 g = email.generator.BytesGenerator(bytesmsg, policy=msg.policy) The problem is that if neither mangle_from_ nor policy arguments are passed to email.generator.BytesGenerator(), then mangle_from_ defaults to True, and the mangle_from_ setting in the message is ignored. This is not really documented: https://docs.python.org/3/library/email.generator.html#email.generator.BytesGenerator If optional mangle_from_ is True, put a > character in front of any line in the body that starts with the exact string "From ", that is From followed by a space at the beginning of a line. mangle_from_ defaults to the value of the mangle_from_ setting of the policy. Where "the policy" refers to the one passed to BytesGenerator(). Note that this section does _not_ state what happens if neither mangle_from_ nor policy are passed to BytesGenerator(). What actually happens is that in that case mangle_from_ defaults to True. (Not a good choice for default, since that's only useful for the one case where you're writing to an mbox file.) However, there is also a misleading sentence later in that same section: If policy is None (the default), use the policy associated with the Message or EmailMessage object passed to flatten to control the message generation. That's only partially true. If you don't pass a policy to BytesGenerator(), only _some_ of the settings from the message's policy will be used. Some policy settings (e.g. mangle_from_) are obeyed when passed to BytesGenerator(), but ignored in the message's policy even if there was no policy passed to BytesGenerator(). The documentation needs to be changed to state that mangle_from_ defaults to True if neitehr mangle_from_ nor policy are passed to BytesGenerator(), and that last sentence needs to be changed to state that when no policy is passed to BytesGenerator() only _some_ of the fields in the message's policy are used to control the message generation. (An actual list of policy fields are obeyed from the message's policy would be nice.) ---------- components: Library (Lib) messages: 402690 nosy: grant.b.edwards priority: normal severity: normal status: open title: SMTP.send_message() does from mangling when it should not versions: Python 3.9 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue45299> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
