How to create a backup .ost file

Question

I am having to recreate my email IMAP account and need to cancel the current email account and recreate. in the proceass i am instructed to creat a backup ;ost file.

I am not sure how to do this.

Answer 1

Hi Sam Barrett,

Welcome to the Microsoft Q&A forum.

I understand what you’re trying to achieve here. When you need to remove and recreate an IMAP account, it’s very reasonable to want a safe backup first so no local data is lost in the process.

I reviewed the Q&A Assist answer provided above, and the guidance is technically correct. For IMAP accounts, the .ost file is a synchronized cache rather than a true backup, and exporting to a .pst file is the appropriate way to create a usable backup before making changes.

Have you had a chance to try the steps in the Q&A Assist answer yet, especially exporting the IMAP data to a .pst file?

In addition to what’s already been shared, I’d like to add a couple of helpful points to keep in mind before you export and recreate the account:

• Before exporting, make sure the folders you need are fully available in Outlook (for example, if Outlook is only caching a limited time range, older items may not be included in the export).
• After you recreate the IMAP account, Outlook will rebuild its local data file during the resync, and you can then open or import the .pst file if you need to bring any items back into Outlook.

If you let me know whether you were able to complete the export, I can share a few additional checks to help ensure the backup and account recreation go smoothly.

I hope this helps.

Answer 2

For an IMAP account, Outlook uses an Offline Outlook Data File (.ost), which is just a synchronized copy of what is on the mail server. It is not necessary to back up the .ost itself, because Outlook will recreate it and re-download the data from the server when the account is set up again.

To protect data before deleting and recreating the IMAP account, export it to a .pst file instead (this is the real backup file Outlook uses):

1. In Outlook, go to File > Open & Export > Import/Export.
2. Choose Export to a file > Next.
3. Select Outlook Data File (.pst) > Next.
4. Select the IMAP account (or specific folders) to back up, and enable Include subfolders.
5. Choose a location and file name for the .pst (for example in Documents\Outlook Files), then select Finish.
6. Optionally set a password for the .pst, or leave it blank and select OK.

This .pst file is the backup. After recreating the IMAP account, it can be opened or imported:

• To open: File > Open & Export > Open Outlook Data File, browse to the .pst, and open it.
• To import (merge into the new account): File > Open & Export > Import/Export > Import from another program or file > Outlook Data File (.pst) and follow the wizard.

If the .ost file is ever damaged or needs to be recreated, Outlook can generate a new one automatically by removing it and letting Outlook resync, or by following the documented steps to re-create an offline Outlook Data File (.ost).

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References:

• Create an Outlook Data File (.pst) to save your information
• About Outlook Data Files (.pst and .ost)
• Open or import items from an offline Outlook Data File (.ost)
• Terminated in error found in Outlook Sync Issues log files
• How do I recover my old email messages, my contacts and everything else I had in Outlook? - Microsoft Q&A