So we just did a pilot group to Office 365 and once our small group was migrated it turns out that users within our organization that use a variety of Office outlook 2010 and 2007 couldn't email and they would receive a bounced message: The recipient's e-mail address was not found in the recipient's e-mail system. Microsoft Exchange will not try to redeliver this message for you. Please check the e-mail address and try resending this message, or provide the following diagnostic text to your system administrator. _____ Sent by Microsoft Exchange Server 2007 So we have an internal 2003 exchange server (primary) and a 2010 exchange server that sync's with the 2007 exchange server fyi. Once we migrated our pilot group members we couldn't receive any emails. We then had to change our accounts to Mail Enabled contacts from our 2010 exchange server but then had the issue described below. What I did to correct this issue is on the user's 2007 outlook changed it from cached exchange mode to noncached and emailed one of our pilot group members with out error. I then changed it back to cached exchange mode and tested successfully again. Anyone know why this would work like this?

Hello, Regarding the O365 questions, please also post it via: Microsoft Online: Exchange Online http://social.technet.microsoft.com/Forums/en-US/onlineservicesexchange/threads Thanks, Simon