Is a list allowed in reply_to field in message?

[thstart]

I want to assign a list to reply_to field in message.

Like this:

reply_tos = ['ema...@gmail.com', 'ema...@gmail.com', 'ema...@gmail.com']

message.reply_to = reply_tos

1) does appengine Email allows this? It is defined in http://www.ietf.org/rfc/rfc0822.txt

4.4.3.  REPLY-TO / RESENT-REPLY-TO

This field provides a general  mechanism  for  indicating  any

        mailbox(es)  to which responses are to be sent.  Three typical

        uses for this feature can  be  distinguished.   In  the  first

        case,  the  author(s) may not have regular machine-based mail-

        boxes and therefore wish(es) to indicate an alternate  machine

        address.   In  the  second case, an author may wish additional

        persons to be made aware of, or responsible for,  replies.   A

        somewhat  different  use  may be of some help to "text message

        teleconferencing" groups equipped with automatic  distribution

        services:   include the address of that service in the "Reply-

        To" field of all messages  submitted  to  the  teleconference;

        then  participants  can  "reply"  to conference submissions to

        guarantee the correct distribution of any submission of  their

        own.

2) if allowed, how long the list can be? 1,000 emails, 2,000?

Thank you in advance,

Regards,

--Constantine