Dear Team,

I am using Office 365 to accessing mails, the problem is i have configured mail through exchange and data file was created as a .OST after few days i have some problem in my system so re configuring the mail but i want to map the existing OST file i don't want to create new ost and downloading mails once second pls help to 

Regards

Vishnu.K

Ph:9659937731

Hi Vishnu.K,

To configure outlook to use an existing .ost file, you can follow below steps:

• Copy the existing .ost file to the new location that you want to use.
• Go to Control Panel\All Control Panel Items, click "Mail" to open "Mail Setup" dialog.
• Click "Show Profiles...", then click "Remove" button to remove the existing profile. (If you have other mail account in this profile, you can choose to add a new profile in this steps)
• "Add Account" dialog will pop up, click "Next" Outlook finds your account information. After Outlook finishes the setup for your account, select the Change account settings option, and then click "Next".
• Select "Change account settings">Next >Server Settings>More Settings>Advanced tab>Outlook Data File Settings
• Browse to the .ost file that you copied in step 1, and then click "OK".
• Click Finish to finish the setup for your email account.

For detailed reference, you can refer to this article: https://support.microsoft.com/en-us/kb/2752583

Hope this helps.

Regards,

Ethan Hua
TechNet Community Support