使用Python3发送UTF-8编码的电子邮件会导致UnicodeError

我期待以下代码发送UTF-8编码的邮件

import email.parser
import smtplib

msg_str = """From: A <a@example.org>
To: B <b@example.org>
Content-Type: text/plain; charset="UTF-8"

Testing UTF-8: – ä."""

msg = email.parser.Parser().parsestr(msg_str)
smtplib.SMTP('localhost').send_message(msg)

这里失败的是在pythons

smtplib

中调用

email.generator.BytesGenerator

。如果

msg

对象不能转换为字节，那么电子邮件解析器不应该首先失败吗

UnicodeEncodeError: 'ascii' codec can't encode character '\u2013' in position 15: ordinal not in range(128)