hi, we have Exchange 2010 and 2003 coexist. just finish configuring Exchange 2010 (CAS/HT combined role, and MBX role on separate server) and testing mail flow. all works ok except for sending meeting/appointment request from Exchange 2010 mailbox to legacy mailbox.Sender will see the item as sent, but recipient never received that. tracking the message, i can see it has been passed from HT to exchange 2003 front end. and tracking further on Exchange System manager (2003), front end has handed the message to back end (mailbox) server, where the tracking ended with message: "SMTP:Message Sent to badmail". that's why the meeting request never gets to destination. Any idea what's causing it? Anywhere to look at? Thanks.

Hi wking10 I want to very some information regarding to your issue. 1. Does the issue occur all the emails which were sent from mailbox on exchange 2010 to mailbox on exchange 2003? 2. Is there any third pary antivirus software install for your exchange 2003 server Other cause maybe the recepient's mailbox/database corrupted, you could create a new mailbox/database and make a test. Regards! Gavin

Hi Gavin, I am still not sure what's causing the issue, but somehow restarting the SMTP service on the 2003 backend server resolved the issue.