Hi guys,

I have a question about performance implications of multiple shared mailboxes running in Outlook.

Users have their primary mailboxes configured for caching (email content only, but not non-email content) with cache hybrid mode enabled (I'm working on disabling it, as well as disabling slow link detection). For users who have only a single (primary) mailbox attached to Outlook, the experience is not that bad.

However, for guys with multiple mailboxes in Outlook (some guys have primary + 3 additional mailboxes) Outlook is not only slow but it often freezes completely (users restart it multiple times, reboot their PCs, log calls with desktop and server support teams etc) - basically the overall experience is terrible. The caching for these shared mailboxes is off (they had issues and disabled caching some times ago without documenting whats and whys - I'm looking into this one as well, as I think it should be on, but maybe keep calendars and other non-email content online). I know that there is a session between Outlook and Exchange for each folder in Outlook and that large number of these session may affect Outlook performances. I'm looking for an advice about this matter and if there is a best practices guide that address and explains the issues with attaching multiple (shared) mailboxes to Outlook and reasons that cause these issues.

I would like to ask if anyone has experience with dealing with multiple shared mailboxes (some are over 100 GB in size) in a hybrid environment as well as in a pure Exchange Online environment (as that's where these guys are heading)?

Another issue that's been detected is a file-level AV client running on PCs without exclusions set for Outlook - I know this can cause issues and I'm going to fix it in the following days.

I'm also working on disabling Outlook hybrid cache mode and detection of slow links.

I also found that large number of items in a folder can affect Outlook performances. I would like to know is this caused by indexing or there is something else and is this related to cached mailboxes only or non-cached ones are affected as well (performance degradation)? If I disable indexing of Outlook content, is it going to affect the search speed or the user won't be able to search the mailbox at all?

Any thoughts please?

Thanks

Zoran

Hi Zoran:

Sorry for the late response.

Indexing can affect outlook performance in some ways. It depends on the shared mailbox configuration and data file size. For example, if the shared mailbox configured as additional mailbox or auto-mapped, the data will be synced to the same .ost file. And if the shared mailbox is large or contains a lot of items. The performance will be affected.

The WDS indexer index is only for cached mailbox. Online mailbox will turn to server side. If you disable the indexing, the index will switch to server side. So user will still be able to search their mailbox.

To improved Outlook performance, following tips might help:

1.  Disable caching of all shared folders
2. Set up separated data file for shared mailbox
3. Reduce the number of folders in the Shared mailbox
4. Reduce the number of items in critical folders
5. Disable email scanners
6. Decrease the synchronization frequency

You can refer KB2297543 and this article to get some ideas.

Thank you.

• Marked as answer by Zoran.M 20 hours 2 minutes ago

Thanks Chloe, much appreciated.