通过 python 处理 email - Email via Python

   Email via Python

  1 MIME - Multipurpose Internet Mail Extensions
 SMTP - Simple Message Transport Protocol

 邮件的发送,
     例子 - send email
         import smtplib
         from email.mime.text import MIMEText
         from email.utils import formatdate, make_msgid
         mess = 'hello there'
         mesgobj = MIMEText(mess)
         mesgobj['To'] = 'testrecevier@example.com'
         mesgobj['From'] = 'testsender@example.com'
         mesgobj['Subject'] = 'Greeting'
         mesgobj['Date'] = formatdate(localtime=1)     # Date header, formatdate() 生成 email 专门日期格式
         mesgobj['Message-ID'] = make_msgid()          # make_msgid() 方法生成唯一的 Message-ID,
         print(mesgobj.as_string())
         print(mesgobj.as_bytes())

         s = smtplib.SMTP('SMTP-SERVER-ADDR')
         s.send_message(mesgobj)
         s.quit()

 邮件的解析,
     例子 - parsing email,
     from email.parser import Parser
     headers = Parser().parsestr(mesgobj.as_string())  # mesgobj 为上例中对象.
     for h,v in headers.items():
         print("Header[%s] - " % h,v)
     print('Emial content - ', mesgobj.get_payload())  # 打印邮件正文.

 带有附件的邮件发送处理 - Packing MIME,
     邮件的附件有 音频, 图像, 压缩文件等等, 通过 python doc 的上的例子看一下儿
     对邮件的附件的处理方式,
     例子 - send email with attachments,
         * an example of how to send the entire contents of a directory as an email message

         import os
         import sys
         import smtplib
         # For guessing MIME type based on file name extension
         import mimetypes
         from optparse import OptionParser
         from email import encoders
         from email.message import Message
         from email.mime.audio import MIMEAudio
         from email.mime.base import MIMEBase
         from email.mime.image import MIMEImage
         from email.mime.multipart import MIMEMultipart
         from email.mime.text import MIMEText

         COMMASPACE = ', '

         def main():
             parser = OptionParser(usage='''\
         Send the contents of a directory as a MIME message.

         Usage: %prog [options]

         Unless the -o option is given, the email is sent by forwarding to your local
         SMTP server, which then does the normal delivery process.  Your local machine
         must be running an SMTP server.
         ''')
             parser.add_option('-d', '--directory',
                               type='string', action='store',
                               help='''Mail the contents of the specified directory,
                               otherwise use the current directory.  Only the regular
                               files in the directory are sent, and we don't recurse to
                               subdirectories.''')
             parser.add_option('-o', '--output',
                               type='string', action='store', metavar='FILE',
                               help='''Print the composed message to FILE instead of
                               sending the message to the SMTP server.''')
             parser.add_option('-s', '--sender',
                               type='string', action='store', metavar='SENDER',
                               help='The value of the From: header (required)')
             parser.add_option('-r', '--recipient',
                               type='string', action='append', metavar='RECIPIENT',
                               default=[], dest='recipients',
                               help='A To: header value (at least one required)')
             opts, args = parser.parse_args()
             if not opts.sender or not opts.recipients:
                 parser.print_help()    # SMTP server 只处理地址有效的 sender 跟 recipients
                 sys.exit(1)
             directory = opts.directory
             if not directory:
                 directory = '.'        # 之前的代码的功能是通过 OptionParser 没款完成对命令行参数的解析
             # Create the enclosing (outer) message
             outer = MIMEMultipart()    # 构建一个带附件的 email 对象
             outer['Subject'] = 'Contents of directory %s' % os.path.abspath(directory)
             outer['To'] = COMMASPACE.join(opts.recipients)
             outer['From'] = opts.sender
             outer.preamble = 'You will not see this in a MIME-aware mail reader.\n'

             for filename in os.listdir(directory):    # 按附件类型做相应的处理
                 path = os.path.join(directory, filename)
                 if not os.path.isfile(path):
                     continue
                 # Guess the content type based on the file's extension.  Encoding
                 # will be ignored, although we should check for simple things like
                 # gzip'd or compressed files.
                 ctype, encoding = mimetypes.guess_type(path) # 附件类型的判断
                 if ctype is None or encoding is not None:
                     # No guess could be made, or the file is encoded (compressed), so
                     # use a generic bag-of-bits type.
                     ctype = 'application/octet-stream'       # zip, pdf 等附件的类型
                 maintype, subtype = ctype.split('/', 1)
                 if maintype == 'text':             # 处理的 文本text 类型的附件
                     fp = open(path)
                     # Note: we should handle calculating the charset
                     msg = MIMEText(fp.read(), _subtype=subtype)
                     fp.close()
                 elif maintype == 'image':          # 处理的 图像image 类型的附件
                     fp = open(path, 'rb')
                     msg = MIMEImage(fp.read(), _subtype=subtype)
                     fp.close()
                 elif maintype == 'audio':          # 处理的 音频audio 类型的附件
                     fp = open(path, 'rb')
                     msg = MIMEAudio(fp.read(), _subtype=subtype)
                     fp.close()
                 else:
                     fp = open(path, 'rb')          # 处理的其他类型的附件:如 zip, pdf 等
                     msg = MIMEBase(maintype, subtype)
                     msg.set_payload(fp.read())
                     fp.close()
                     # Encode the payload using Base64
                     encoders.encode_base64(msg)
                 # Set the filename parameter
                 msg.add_header('Content-Disposition', 'attachment', filename=filename)
                 outer.attach(msg)
             # Now send or store the message
             composed = outer.as_string()
             if opts.output:                        # 保存到文件 store
                 fp = open(opts.output, 'w')
                 fp.write(composed)
                 fp.close()
             else:
                 s = smtplib.SMTP('localhost')      # SMTP server 发送处理
                 s.sendmail(opts.sender, opts.recipients, composed)
                 s.quit()

         if __name__ == '__main__':
             main()

 MIME 的解包 - Unpacking MIME

     接收方对收到的 MIMEMultipart 的处理,
         '''Unpack a MIME message into a directory of files.'''

         import os
         import sys
         import email
         import errno
         import mimetypes
         from optparse import OptionParser
         def main():
             parser = OptionParser(usage='''\
             Unpack a MIME message into a directory of files.

             Usage: %prog [options] msgfile
             ''')
             parser.add_option('-d', '--directory',
                               type='string', action='store',
                               help='''Unpack the MIME message into the named
                               directory, which will be created if it doesn't already
                               exist.''')
             opts, args = parser.parse_args()
             if not opts.directory:
                 parser.print_help()
                 sys.exit(1)

             try:
                 msgfile = args[0]
             except IndexError:
                 parser.print_help()
                 sys.exit(1)

             try:
                 os.mkdir(opts.directory)
             except OSError as e:
                 # Ignore directory exists error
                 if e.errno != errno.EEXIST:
                     raise

             fp = open(msgfile)
             msg = email.message_from_file(fp)
             fp.close()

             counter = 1
             for part in msg.walk():
                 # multipart/* are just containers
                 if part.get_content_maintype() == 'multipart':
                     continue
                 # Applications should really sanitize the given filename so that an
                 # email message can't be used to overwrite important files
                 filename = part.get_filename()
                 if not filename:
                     ext = mimetypes.guess_extension(part.get_content_type())
                     if not ext:
                         # Use a generic bag-of-bits extension
                         ext = '.bin'
                     filename = 'part-%03d%s' % (counter, ext)
                 counter += 1
                 fp = open(os.path.join(opts.directory, filename), 'wb')
                 fp.write(part.get_payload(decode=True))
                 fp.close()

         if __name__ == '__main__':
             main()

 Reference,
     https://docs.python.org/3/library/email.html