Invited Participants email notification problem

PHP Version: 5.1.4
MySQL Version: 5.0.21
Web Server: Apache 2.2.2
Browser: Firefox 2.0.0.4 & IE 6.0.2900.218.xpsp_gdr.070227-2254CO
phpscheduleit: 1.2.7

Description
We are using this calendar for managing allocation of network engineers. A user will create a reservation selecting a resource. The admin will then modify the reservation and add paticipants dependant on the network engineer working that resource. The admin will then approve the reservation.

The user that creating the resource receives the notifications with no problem however the invited participants don't receive an email. Instead the admin receives a notification that the email could not be delivered. It appears that the user memberid from the login table is being added to the front of their email address ... eg sc14668e7119eea5|t472554@xtra.co.nz, this causes the below response from that users smtp server.

   Reporting-MTA: dns; ish7.******.co.nz
   X-Postfix-Queue-ID: 83D8486A
   X-Postfix-Sender: rfc822; ******@*******.co.nz
   Arrival-Date: Mon, 11 Jun 2007 15:08:16 +1200 (NZST)

   Final-Recipient: rfc822; sc14668e7119eea5|t472554@xtra.co.nz
   Original-Recipient: rfc822;sc14668e7119eea5|t472554@xtra.co.nz
   Action: failed
   Status: 5.0.0
   Remote-MTA: dns; 210.54.141.2
   Diagnostic-Code: smtp; 550 Invalid recipient:
    <sc14668e7119eea5|t472554@xtra.co.nz>

We are really keen to use this as it solves a huge problem within our business for management and reservation of this resource. Any ideas on where we might have gone wrong or is this a bug?

Cheers
Donald