Said It Here

How to fix sync problems on large Outlook mailboxes

Excessive mailbox size, high item counts, and deep folder structures cause Outlook to fail to synchronize properly because users treat mailboxes like filing cabinets. While switching shared mailboxes to online-only mode can resolve these sync failures, large mailboxes continue to suffer from severe performance bottlenecks.

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

  1. 1
    Setting shared mailboxes to online mode only
  2. 2
    Caching less offline data such as 3 months instead of 1 year
  3. 3
    Using Outlook webmail or the new client
  4. 4
    Moving items to archives or SharePoint
  5. 5
    Rebuilding the .ost file
  6. 6
    Updating to the latest version of Office
  7. 7
    Ensuring advanced logging is disabled
  8. 8
    Running outlook.exe /cleanviews
  9. 9
    Switching to the new Outlook
  10. 10
    Viewing the mailbox in OWA and permanently deleting the problematic syncing item

In their words

Unedited, most upvoted first, each linked to the thread it came from.

“I have recently been working with a client getting a ton of these Synchronization Log emails in their Deleted folder in Outlook.”source ↗

“Well I just had another client put in a ticket for the exact same thing.”source ↗

Any_Professional5587 · r/sysadmin · 4 upvotes

“For a shared mailbox, we have set it to online mode only which has resolved our sync issue. The problem as you know is that people still use it as a filing cabinet.”source ↗

vivkkrishnan2005 · r/sysadmin · 1 upvotes

“Since a while we are experiencing synchronisation problems on mailboxen. These mailboxes are quite large. What are the criteria to avoid sync problems?”source ↗

HugeGuava2009 · r/sysadmin

Where this came up

r/sysadminemail managementit supporttroubleshooting

People with this problem also raised