How to Resolve Outlook Error 0x00040820 Message

Suppose you are trying to synchronize the .ost file in Outlook 2002 with Exchange Server which has reached 2GB file size limitation, it may results in following error message.

“Task Microsoft Exchange Server reported error (0x00040820): Errors in background synchronization. In most cases, further information is available in a synchronization log in the Deleted items folder.”

This problem is commonly known as oversized OST file issue. In a case when the ost file reaches its file size limit, you are unable to access all the emails and other data saved in the OST file. The OST files becomes inaccessible in Outlook 2002 and earlier versions, as soon as it reaches the size of about 1.82 GB. In this case you can take some precautions such as reducing the ost file size because MS Outlook and Exchange Server do not have any built-in tool or feature that can resolve the over sized ost file issue.


This error message occurs because OST file in Outlook 2002 and early versions has 2GB file size limitation


Follow any of below mentioned steps to resolve the problem:

1. Permanently delete all the unwanted items from the server based email folders.

2. Move data from any synchronized folder to a non-synchronized folder on the Exchange Server.

3. Move data from a synchronized folder to a personal folders (.pst) file, and permanently delete the data from the synchronized folder.

Run scanost.exe utility to remove the extra space created due to permanently deleted data. But if in case there is no extra space due to deleted items, the scanost.exe utility will not work.

Where to search for scanost.exe file: C:\ Documents and Settings\ username\ Local Settings\ Application Data\ Microsoft\ Outlook\ outlook.ost

It is not always possible to permanently delete items from your server mailbox, in such a case manually convert ost to pst file. Third party ost to pst converters are available to convert ost file to pst file, the resulting PST file can be imported to MS outlook directly. OST to PST conversion software uses advance scanning techniques to convert damaged or corrupt Outlook ost to pst file. Such tools are read only i.e. do not alter original ost file contents. OST converter Software supports MS Outlook and is compatible with Windows 10, Windows 8, Windows 7, Vista and Windows XP.