Anybody ever experience issues with read receipts and Outlook 2000 email clients? I have successfully processed read receipts for an account on other mail clients, including Outlook Express on the very same machine with the very same mail account, but as soon as you attempt it with an Outlook 2000 mail client, forget it, it fails with the following error message: The message could not be sent because it rejected you as the sender. Server Response: "550 SMTP Envelope Sender must be valid'. (Account: 'mail.example.com', SMTP Server: 'mail.example.com', Error Number: 0x800ccc78).
Funny thing is, for some mail servers, Outlook 2000 will process the read receipts, certain others, forget it. My troubleshooting efforts so far seem to be something with the "postmaster" account and bounce email setups being different.
Does anybody have any definitive research/answers to the issue?