code: async def mail(self, sender, options=None):
          
          if options is None:
              options = []
  
          from_addr = "FROM:{}".format(quoteaddr(sender))
          code, message = await self.do_cmd("MAIL", from_addr, *options)
  
          return code, message
docs: Sends a SMTP 'MAIL' command. - Starts the mail transfer session.
  
          For further details, please check out `RFC 5321 § 4.1.1.2`_ and
          `§ 3.3`_.
  
          Args:
              sender (str): Sender mailbox (used as reverse-path).
              options (list of str or None, optional): Additional options to send
                  along with the *MAIL* command.
  
          Raises:
              ConnectionResetError: If the connection with the server is
                  unexpectedely lost.
              SMTPCommandFailedError: If the MAIL command fails.
  
          Returns:
              (int, str): A (code, message) 2-tuple containing the server
                  response.
  
          .. _`RFC 5321 § 4.1.1.2`: https://tools.ietf.org/html/rfc5321#section-4.1.1.2
          .. _`§ 3.3`: https://tools.ietf.org/html/rfc5321#section-3.3