Article ID: 161889
This article provides a quick reference for troubleshooting Microsoft Exchange client offline folders (.ost files).
DefinitionsOST - Offline Folder Storage - A file that contains a local replica of a user's Microsoft Exchange Server-based folders (private and public) and forms. The OST is synchronized with the Microsoft Exchange Server copy for use while working offline. An OST is specific to a particular mailbox and cannot be accessed by other users of Microsoft Exchange Server.
PST - Personal Folder Storage - A file that may contain folders, messages, forms, files and other items. You can create any number of PSTs for use with a single profile. You can also designate a PST as the delivery location for incoming mail.
New Client Installation - If you are installing the Microsoft Exchange client for the first time, during the profile creation you will be asked if you travel with the computer. If you answer yes, an Offline Store provider is set up for you and a file, Exchange.ost, is created. The OST is where the offline folders will be stored.
Existing Client Installation - If this is an existing installation of the Microsoft Exchange client, you can create an offline store using the Offline Folder File Setting button in the Advanced tab of the Microsoft Exchange Server driver property page. If multiple users will be using a single computer, each user needs his or her own OST file.
Creating an OSTHow to make a server-based folder available for offline use:
How to disable an OST:
An OST is the preferred method for offline storage, because it allows you to use public folders and organizational forms while you work offline. Because an OST acts as a copy of Microsoft Exchange Server-based folders, the data is backed up during the standard Microsoft Exchange Server backup procedures.
NOTE: The OST is a replica. It is not a backup, and cannot be restored.
A local PST must be backed up by the individual owner. One advantage a PST has is the ability to use the remote e-mail features of the Microsoft Exchange Client, download headers, move or copy messages, delete unwanted messages before downloading, and read new messages while others are downloading. When you use an OST, the synchronization process is not multi-threaded.
OST Sync Log:
During the OST synchronization process, a log file is kept, and it is placed in the Deleted Items folder at the completion of synchronization. This log file is very useful in determining synchronization details and error messages. The following are some of the error messages and possible causes:
8004010f - This error message may be caused by any of the following reasons:
80040115 - A network error prevented successful completion of the operation. Complete some basic remote procedure call (RPC) network troubleshooting.
User's mailbox deleted from Microsoft Exchange Server:
Because an OST is stamped with a mailbox's unique ID, if a user's mailbox is deleted and re-created on the computer running Microsoft Exchange Server, the OST file does not synchronize with the new mailbox. The only way to recover the data in the OST is to use the following steps exactly before starting the client online:
Article ID: 161889 - Last Review: June 22, 2014 - Revision: 4.0
Retired KB Content Disclaimer
This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.