[horde] Can't send to BCC or CC without To: using activesync

[Brent]

  Trying to send an email with ONLY the BCC field filled out using  
ActiveSync.  Device says "the message was rejected by the server".   
Same happens with CC-only filled out and omitting the To: field.

Checking the horde logs, I find:

NOTICE: HORDE PHP ERROR: Undefined index: To [pid 1278 on line 305 of  
"/usr/share/pear/Horde/Core/ActiveSync/Mail.php"

Line 305 is this:
 $recipients = $h_array['To'];

Function area:

 protected function _sendRaw()
    {
        $h_array = $this->_headers->toArray(array('charset' => 'UTF-8'));
        $recipients = $h_array['To'];
        if (!empty($h_array['Cc'])) {
            $recipients .= ',' . $h_array['Cc'];
        }
        if (!empty($h_array['Bcc'])) {
            $recipients .= ',' . $h_array['Bcc'];
            unset($h_array['Bcc']);
        }

Seems that $h_array['To'] is undefined and it bombs out?

Not sure of the proper fix for this.  I can send email using Horde/Imp  
with only the CC or BCC field filled out, this only seems to be  
happening using an ActiveSync device.

brent