How to Back Up IMAP Emails from Classic Outlook to a PST File

Quick Answer

You can back up emails from an IMAP account configured in Classic Outlook for Microsoft 365 by exporting the mailbox folders to an Outlook Data File (.pst). The PST file stores a local copy of the selected emails, including their attachments and subfolders, which can be accessed later using Outlook.

To create the backup, open Outlook and select File > Open & Export > Import/Export > Export to a file > Outlook Data File (.pst). Select the IMAP account or required folders, enable Include subfolders, choose a destination, and complete the export.

What Is an Outlook PST Backup?

An Outlook Data File (.pst), also known as a Personal Storage Table, is a local file used to store copies of Outlook emails and other supported Outlook items.

IMAP synchronizes email between the mail server and Outlook. However, synchronization is not the same as maintaining an independent backup. If an email is deleted from the server and that deletion synchronizes with Outlook, the message may also disappear from the synchronized mailbox.

Exporting the mailbox to a PST file provides an additional local copy that can be opened in Outlook later, even when the original mailbox is no longer available.

What Does the PST Backup Include?

When exporting email folders from Classic Outlook, the PST file can contain:

• Email messages in the selected folders.
• Email attachments.
• Sent Items and other selected mail folders.
• Custom folders and their subfolders, when Include subfolders is enabled.
• Other Outlook items supported by the selected account and export operation.

The export creates a copy of the selected information. It does not delete the original messages from the IMAP server or Outlook.

Outlook does not export certain configuration information, such as message rules, blocked senders lists, folder views, folder permissions, and AutoArchive settings.

Prerequisites Before Taking the Backup

Before exporting the IMAP mailbox, complete the following checks to reduce the possibility of missing emails in the backup.

1. Use Classic Outlook for Windows

The procedure in this article is for the desktop version of Classic Outlook for Windows, not Outlook on the web.

Classic Outlook has a traditional File menu in the upper-left corner of its ribbon. New Outlook has a different interface and export procedure.

2. Allow IMAP Synchronization to Complete

Make sure Outlook has finished downloading and synchronizing the required email folders before starting the export.

• Check that Inbox, Sent Items, and other required folders are visible.
• Confirm that older messages are available, not just recently received emails.
• Allow large folders and attachments sufficient time to synchronize.
• Check Outlook's synchronization status for errors or pending operations.
• Compare important folders with the corresponding folders in your webmail account when possible.

If Outlook has not downloaded the complete mailbox, the exported PST may not contain every message available on the IMAP server.

3. Check the Available Synchronization Period

Some Outlook account configurations limit how much email is synchronized locally. Microsoft documents a default one-year download period for certain Outlook configurations.

In Classic Outlook, check the following location if the synchronization-period setting is available for your account:

File > Account Settings > Account Settings > select the account > Change or Sync Settings.

If a Mail to keep offline or synchronization-period slider is available, select All when you need to download the complete available email history.

The available settings depend on the account type and Outlook configuration. Do not assume that every IMAP account provides the same synchronization controls. Allow any required synchronization to finish before exporting.

4. Prepare a Backup Destination

Ensure that the computer has enough free storage space for the PST file. For a large mailbox containing many attachments, the backup file may require considerable disk space.

Choose a suitable local folder or an external storage device. Avoid exporting an actively used PST directly into a OneDrive-synchronized folder. Microsoft advises against this because OneDrive can block automatic synchronization of Outlook PST files.

How to Back Up IMAP Emails from Classic Outlook to a PST File

Follow these steps to export the IMAP mailbox into a local Outlook Data File.

Step 1: Open Classic Outlook

Launch Microsoft Outlook on your Windows computer and wait until the required IMAP account and its folders have synchronized.

Step 2: Open the Import and Export Wizard

1. Click File in the upper-left corner.
2. Select Open & Export.
3. Click Import/Export.

The Import and Export Wizard will open.

Step 3: Select Export to a File

1. Select Export to a file.
2. Click Next.

Step 4: Select Outlook Data File (.pst)

1. Select Outlook Data File (.pst) from the available file types.
2. Click Next.

Outlook will display the available accounts and folders that can be exported.

Step 5: Select the IMAP Account or Required Folders

You can export the entire IMAP mailbox or select individual folders, depending on your backup requirements.

To back up the complete IMAP mailbox:

1. Locate the required IMAP account in the folder selection window.
2. Select the account's top-level entry rather than selecting only the Inbox.
3. Enable the Include subfolders checkbox.
4. Click Next.

To back up selected folders only:

1. Expand the IMAP account folder structure.
2. Select the required folders, such as Inbox, Sent Items, or custom folders.
3. Enable Include subfolders if you also need the folders nested under the selected folder.
4. Click Next.

For a complete email backup, selecting the account's top-level entry and including its subfolders is generally the appropriate approach.

Step 6: Choose the PST Backup Location

1. Click Browse.
2. Navigate to the folder where you want to save the backup.
3. Enter a meaningful file name, for example IMAP_Email_Backup_2026.pst.
4. Click OK to confirm the destination.
5. Click Next.

For better backup management, use a descriptive file name containing the account name or backup date. Avoid using a folder that is actively synchronized by OneDrive.

Step 7: Complete the Export

1. Review the export options.
2. Click Finish.
3. If Outlook prompts you to create an Outlook Data File password, you can enter and confirm an optional password or leave the password fields blank if you do not want password protection.
4. Allow Outlook to complete the export.

The export may take several minutes or considerably longer for a large mailbox. Do not close Outlook or interrupt the operation while it is running.

After the export finishes, the PST file will be available at the destination you selected.

How to Verify the PST Backup

Do not assume that a backup is complete simply because Outlook has created a PST file. Open the exported file and check its contents before relying on it.

Step 1: Open the Exported PST File

1. Open Classic Outlook.
2. Click File.
3. Select Open & Export > Open Outlook Data File.
4. Browse to the location where the PST backup was saved.
5. Select the PST file and click Open.

The PST file will appear as a separate data file in Outlook's folder navigation pane.

Step 2: Check the Email Folders

Expand the newly opened PST file and inspect the folders.

• Confirm that the expected folders are present.
• Open Inbox and check older and newer messages.
• Check Sent Items and important custom folders.
• Open several messages to verify their contents.
• Open important attachments to confirm they are accessible.

For important mailboxes, compare the exported messages with the original IMAP mailbox, particularly the oldest messages and folders that contain critical business information.

Step 3: Keep an Additional Copy

After verifying the PST file, close Outlook or close the PST data file in Outlook before copying it to another storage location.

Maintain another copy on an external hard drive or another secure backup destination. If using cloud storage, upload the closed PST as a backup copy rather than actively opening and modifying the PST from a synchronized folder.

How to Access or Restore Emails from a PST Backup

A PST backup can be used to access old emails or recover messages when required. There are two different approaches, depending on whether you want to browse the backup or restore messages into a mailbox.

Option 1: Open the PST Without Importing Emails

If you only want to read old emails, search for messages, or retrieve attachments, there is no need to import the entire PST into your mailbox.

1. Open Classic Outlook.
2. Go to File > Open & Export > Open Outlook Data File.
3. Select the required PST file.
4. Click Open.
5. Expand the PST file in the folder navigation pane.
6. Browse the required folders and open the messages.

This method allows you to access the stored emails without copying them back into the IMAP mailbox.

Option 2: Import Emails into an Outlook Mailbox

If you want to restore messages into an existing IMAP account or another Outlook mailbox, use the Import and Export Wizard.

1. Open Classic Outlook.
2. Select File > Open & Export > Import/Export.
3. Select Import from another program or file and click Next.
4. Select Outlook Data File (.pst) and click Next.
5. Browse to the backup PST file.
6. Select the appropriate duplicate-handling option.
7. Click Next.
8. Select the folder or mailbox where you want to restore the messages.
9. Click Finish to begin the import.

Wait for Outlook to complete the import. If the destination is an IMAP mailbox, restored messages may need to synchronize with the mail server. Make sure the destination mailbox has sufficient storage space and that you have permission to add messages to it.

Important: Importing a PST into a mailbox is different from simply opening the PST. Importing copies selected messages into the destination mailbox and may create duplicates if the same messages already exist.

Common Problems During Outlook PST Export

1. Older Emails Are Missing from the PST File

Possible cause: Outlook had not downloaded the complete email history before the export, or the account's synchronization settings limited the locally available messages.

What to do:

• Check the original mailbox using webmail.
• Review the synchronization settings available for the account.
• Allow older messages and attachments to download.
• Check the affected folders again.
• Repeat the export after synchronization has completed.

2. Some Email Folders Are Missing

Possible cause: Only selected folders were exported, or the Include subfolders option was not enabled.

What to do:

• Repeat the export procedure.
• Select the account's top-level entry if you need the complete mailbox.
• Enable Include subfolders.
• Verify that the required folders are visible in the exported PST.

Also check whether the missing folders are available and synchronized in the original IMAP account.

3. PST Export Is Taking Too Long

Possible cause: The mailbox contains a large number of messages, large attachments, or folders that have not finished synchronizing.

What to do:

• Allow Outlook sufficient time to complete the operation.
• Check the available disk space.
• Ensure that the computer does not enter sleep mode.
• Check Outlook for synchronization or connection errors.
• Consider exporting particularly large mailboxes in separate folder groups if the full export repeatedly encounters problems.

4. PST File Cannot Be Opened

Possible cause: The PST file may be incomplete, damaged, password-protected, or stored at a location that is no longer accessible.

What to do:

• Check whether the file exists at the expected location.
• Confirm that the file has a .pst extension.
• Check whether the file is password-protected and enter the correct password.
• Copy the file to a local drive if it is being accessed from removable storage.
• If Outlook reports that the data file is damaged, consult Microsoft's PST repair guidance before attempting recovery.

Important Limitations of PST Backups

Before relying on PST exports as your email backup strategy, understand the following limitations:

• Not an automatic backup: Exporting to PST creates a snapshot of the selected Outlook data at that time. New emails received later are not automatically added to the existing backup.
• Synchronization dependency: Messages that have not been downloaded or synchronized may be absent from the export.
• Configuration is not included: Outlook rules, blocked senders lists, folder views, and certain other settings are not included.
• Storage requirements: Large PST files require sufficient disk space and appropriate storage management.
• File protection: A PST may contain confidential business or personal information. Store it securely and use appropriate encryption and access controls for sensitive backups.
• Separate backup copies: Keeping the only PST file on the same computer as the original mailbox does not protect against every hardware failure, theft, ransomware incident, or accidental deletion.

For important business mailboxes, maintain multiple backup copies on separate storage devices or approved backup destinations. Repeat the export periodically to capture newly received messages.

Frequently Asked Questions

Does exporting IMAP emails to PST delete emails from the mail server?

No. Outlook creates a copy of the selected messages in the PST file. The original emails remain in the IMAP mailbox unless they are separately deleted or moved.

Will the PST backup include email attachments?

Yes. Outlook includes email attachments when exporting messages to a PST file. It is still advisable to open important messages and attachments after exporting to verify that they are accessible.

Can I back up only the Inbox instead of the entire IMAP mailbox?

Yes. In the Import and Export Wizard, select the Inbox folder instead of the account's top-level entry. Enable Include subfolders if you also want to export the folders nested under Inbox.

Can I open the PST file on another computer?

Yes. You can copy the PST file to another computer and open it using a compatible version of Outlook that supports PST files. In Classic Outlook for Windows, use File > Open & Export > Open Outlook Data File.

Can I use a PST backup without an active internet connection?

Yes. Once the PST file has been successfully created and is available locally, you can open and browse its stored messages in Classic Outlook without connecting to the original IMAP mail server. However, internet access may still be required for certain online services or linked content.

Can I use the same PST file for daily or automatic backups?

A PST export is not an automatic synchronization or continuous backup process. You can perform another export periodically, but Outlook does not automatically append every new IMAP message to an existing PST through the standard export wizard. Use a suitable backup solution if automated and scheduled mailbox backups are required.

Can I open a PST backup in New Outlook?

New Outlook for Windows supports accessing PST email data and exporting mailbox data to PST, subject to its documented requirements and limitations. Opening a PST requires Classic Outlook to also be installed with the same 32-bit or 64-bit architecture. For importing mailbox data from a PST, use Classic Outlook for Windows.

Sources

• Microsoft Support – Export emails, contacts, and calendar items to Outlook using a .pst file
• Microsoft Support – Back up your Outlook email
• Microsoft Support – Open and find items in an Outlook Data File (.pst)