Hi guys,

Do you have any advice, or if you could point to a best practice doco, about performance issues with Outlook hosting multiple shared mailboxes?

It's a hybrid environment where primary mailboxes with caching enabled for email content only sit in Exchange Online, while shared mailboxes with disabled caching are still hosted in an on-premise Exchange 2010. Clients use both Outlooks 2010 and 2013. The number of attached shared mailboxes varies between 1 and 3, and the size of these mailboxes goes between 10 and 150 GB. The issues are slow loading of Outlook, occasional freezes and long waiting for a message to open or to be moved between folders.

Also, are there any issues with caching shared mailboxes, as it seems that some users reported certain inconsistencies - it happened a while ago and was not documented well, but I assume it was related to calendars? Would caching "email content only" prevent issues with calendaring in shared mailboxes without causing issues with email content?

Thanks

Zoran

It surprises me that you put user mailboxes in Exchange Online and shared mailboxes on premises since shared mailboxes are free.

A problem with shared mailboxes is what's known as a race condition, where two users concurrently modify the same message, resulting in the last save wiping out the changes of the other user.  This condition is much worse in cached mode because of the latency of the write-back of data.

Thanks Ed. Actually the shared mailboxes in question are online as well. Obviously I was not involved in the transition and I misunderstood what's still on-premises. There are some shared mailboxes still on-premises, but these are accessed by external clients through XenApp and are not part of the performance story.

Okay, so we're better off with keeping shared mailboxes online. Is there anything at the client side we can do to improve Outlook performance? I think the main cause of Outlook performance issues are link latency and server response time, but I wasn't able to find any info on how client side Windows indexing affects an online mailbox?

Thanks

All I can think of is to improve your Internet connection speed and reduce the latency to Office 365.  Try removing any proxy servers you might have in place between clients and Exchange Online.

Thanks Ed, that a good idea. I'm going to check the latency for an on-LAN Outlook and another one connected directly to the internet.

Thanks