您应该将 'utf-8' 参数添加到您的 MIMEText 调用中(它假定 'us-ascii' 默认).

You should just add 'utf-8' argument to your MIMEText calls (it assumes 'us-ascii' by default).

例如:

# -*- encoding: utf-8 -*-

from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText

msg = MIMEMultipart("alternative")
msg["Subject"] = u'テストメール'
part1 = MIMEText(u'u3053u3093u306bu3061u306fu3001u4e16u754cuff01
',
                 "plain", "utf-8")
msg.attach(part1)

print msg.as_string().encode('ascii')