For instance, setting the value to 4 will trigger a full download when the incremental update is larger than one-fourth the size of the full OAB. Updating Outlook manually Even though Outlook is the last in the chain, it is often the first level where the troubleshooting takes place as usually this is where the request is coming from. So I think the reason that cleanup old OAB files can fix it as the current workaround. This allows you to abort the update process when you are for instance on a slow or expensive connection. Provide a name for the group.