I am using ms office outlook 2007 ,2010 . My all mail download from web mail. If take pst file backup & restore.But when download mail from web duplicate mail download same name & folder.

How to prevent duplicate download  mail msoutlook.

If take pst file backup & restore.

Basically, when taking a backup of PST file, there is no "restore" step. May I know why you restored your data? How did you restore the data?

Duplicate emails could be caused by several reasons, such as:

Rules

Multiple accounts

Profile recreation

Synchronization tools

Virus scanner/firewall

Tools to clean up the mess

To prevent or remove the duplicate, please have a look at the following article:

http://www.howto-outlook.com/faq/duplicates.htm

Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

You can use the tools listed in the article to remove duplicate emails.

If I've misunderstood something, please feel free to let me know.

Regards,

Steve Fan
TechNet Community Support

If its an exchange connection, my suggestion is below..

Some time it happens when Cache mode in outlook option in no ticked. Account settings ->Properties-> under the server name ticket "Use cached mode exchange