def send_message(msgstr, from_addr, *to_addrs)
      raise IOError, 'closed session' unless @socket
      mailfrom from_addr
      rcptto_list(to_addrs) {data msgstr}
    end
Sends +msgstr+ as a message.  Single CR ("\r") and LF ("\n") found
in the +msgstr+, are converted into the CR LF pair.  You cannot send a
binary message with this method. +msgstr+ should include both
the message headers and body.

+from_addr+ is a String representing the source mail address.

+to_addr+ is a String or Strings or Array of Strings, representing
the destination mail address or addresses.

=== Example

Net::SMTP.start('smtp.example.com') do |smtp|
smtp.send_message msgstr,
'from@example.com',
['dest@example.com', 'dest2@example.com']
end

=== Errors

This method may raise:

* Net::SMTPServerBusy
* Net::SMTPSyntaxError
* Net::SMTPFatalError
* Net::SMTPUnknownError
* Net::ReadTimeout
* IOError