Jetpack Post by Email not posting emails from mailing list

Howdy!

I’m trying to set up JP’s Post by Email to post emails sent to a mailing list. I’ve conducted several tests:

1. Sending an email to the generated post.wordpress.com address from an address other than my wp.com address.
2. Sending an email to other recipients, including the post.wordpress.com address.
3. Sending an email where all recipients were in the BCC field.
4. Created a mailing list and subscribed the post.wordpress.com address as well as other addresses.

#1-3 posted. And yeah, I know, keep the post.wordpress.com address secret. I sent these to my other email addresses.
#4 The “welcome to the mailing list” email posted, but emails sent to the mailing list did not.

Is this intentionally unsupported?

I’ve followed the troubleshooting steps outlined here before posting. The XML-RPC test fails using the Jetpack Debug Test, but when I manually run

curl -d '<methodCall><methodName>demo.sayHello</methodName></methodCall>' http://news.sisr-issr.org/xmlrpc.php
from my computer, I get the expected result:

<?xml version="1.0" encoding="UTF-8"?>
<methodResponse>
  <params>
    <param>
      <value>
      <string>Hello!</string>
      </value>
    </param>
  </params>
</methodResponse>

I also get the expected “XML-RPC server accepts POST requests only.” message when navigating to http://news.sisr-issr.org/xmlrpc.php, so I’m not quite sure why the Jetpack Debug Test fails. Disabling all my plugins does not affect the results, and I am using Twenty Eleven, Version 1.5.

I’d appreciate any help you can offer. Let me know if I can provide any more details.

All the best,

-Luis

http://wordpress.org/plugins/jetpack/