This article was previously published under Q288283
When the size of your offline files (.ost) or personal folders (.pst) files approaches 2 gigabytes (GB), you may not be able to add more data to the .pst file or the .ost file.
If you try to synchronize an .ost file from a mailbox that is larger than 2 GB, the .ost file stops accepting data, and you may receive the following error message:
Errors in background synchronization. In most cases, more information is available in a synchronization log in the Deleted Items folder.
When you open the synchronization log that is located in your Deleted Items folder, the following information appears:
15:19:28 Synchronizing Mailbox '<username>'15:19:28 Synchronizing Folder 'Outlook Security Settings'15:19:28 Error synchronizing folder15:19:28 [8004060C-53F-0-550]15:19:28 The OST has reached its maximum size. To reduce the amount of data in this OST, start Outlook in offline mode, select someitems that you no longer need, permanently ( press SHIFT + DEL) delete them, then re-sync this folder.15:19:28 Microsoft Exchange Server Information Store15:19:28 For more information on this failure, click the URL below:15:19:28 http://www.microsoft.com/support/prodredirect/outlook2000_us.asp?err=8004060c-53f-0-55015:19:28 Synchronizing Views0c-53f-0-55015:19:28 Done15:19:29 Microsoft Exchange offline address book15:19:29 Download successful
Offline files (.ost) are limited to approximately 2GB in size. The is the same limitation as a personal folders (.pst) file. If you try to add data to an .ost file or a .pst file that is at its size limit, you receive the following error message:
Can't copy the item.
You cannot synchronize Outlook completely until the .ost file size has been reduced to less than 2 GB. You can do this by moving some of the .ost file data to a .pst file, or you can delete data that you do not need from the .ost file. After you move or delete the .ost data, compact the .ost file or the .pst file before you proceed.
Note Microsoft Office Outlook 2007 and Microsoft Office Outlook 2003 can use a new Unicode file format that can exceed this 2 GB limit. For more information about Outlook data file formats, click the following article number to view the article in the Microsoft Knowledge Base:
841207 An Outlook 2003 cached offline folder file is created in ANSI format instead of in Unicode format in Exchange 2003 or in Exchange 2000
For more information about how to compact Outlook data files, click the following article number to view the article in the Microsoft Knowledge Base:
289987 How to compact PST and OST files to eliminate deleted item space in Outlook 2002 and Outlook 2003