We have a user that has Outlook 2011 running. She has an assistant that schedules appointments using a PC with Outlook 2010. She also has an Iphone that is being synched via the Exchange server. An interesting phenomenon is occurring. The Outlook 2010 machine has duplicates, any PC with Outlook 2010 that opens her calendar sees duplicates. However on the Mac and 2011 there are no duplicates. AND any Mac that opens the shared calendar does NOT see duplicates. Also some appointments are disappearing for no reason that has been found as of yet. Have removed and rebuilt the profile on the Outlook 2010 machine. This is driving me insane, any ideas?

Hello, Firstly, as for the best practice for calendar delegates, it is recommended to use the same Outlook version for both manager and delegate. How about check the calendars via OWA? Try running “Outlook /cleanfreebusy” on the problematic clients and see if it works. Thanks, Simon

Simon, Thanks for the information. It would be great to be able to have the same clients on all, I say all because the problematic manager calendar is actually delegated to 7 other users to put information on the calendar. I have actually taken the profile off of the client and restored the profile, with no change. I do find it fascinating that no Macs running 2011 see the duplicates, but the Outlook 2010 clients do. IS there a difference in the way that Exchange handles the connection between them (I know on our servers the Macs are using EWS)

Hello, Yes, Outlook 2010 and 2011 both use the EWS to retrieve user’s free/busy information. If we can see the right calendar items both on Outlook 2011 and OWA, it seems this should be a Outlook client side issue. To further confirm the calendar items are fine in the user’s mailbox, you can also check it with the MFCMAPI tool: http://www.microsoft.com/DownLoads/details.aspx?familyid=55FDFFD7-1878-4637-9808-1E21ABB3AE37&displaylang=en Thanks, Simon

Simon, Thanks for continuing to assist. The MFCMAPI tool is something I have never used so I will have to look into it. I am desktop support, so I will pass this along to our server admins as well. I am still baffled by the duplicates in Outlook 2010 and not in Outlook 2011. I also have not found how to clean the freebusy information on a Mac as well. I too thought it was a client side issue and it still may be. But I have opened the calendar on four different machines (two Macs, and two PC) and get the exact same results. On the Mac, no duplicate, on the PC's duplicates, sometimes triplicates.

The issue was resolved by completely removing the email configuration and files off of the I-phone, re-establishing the email client settings and making sure that no other email synch program was running on the phone. Also did get the computers that were delegates to as close as possible with Office versions (Outlook 2010 and Outlook 2011 on the Macs). Thanks for your help sorry it took me so long to mark this as answered.