How to Fix Attachment Loss During OLM to PST Conversion

You complete the conversion of an OLM file to PST. You open the converted mailbox in Outlook and everything looks fine at first. The folders are present. Email is not secure. Dates and sender names look OK.

Then you open an important message and notice that something’s missing — the attachment.

Maybe it was a PDF invoice, an Excel report, a Word document or an image sent to us by a client. Sometimes it’s just a few attachments that go missing. In some cases, there are dozens of emails with attachments, but the files cannot be opened.

Remember that during the OLM to PST conversion, loss of attachments is a major concern, more so when migrating the mailbox data from Outlook for Mac to Outlook for Windows. You can try to diagnose the problem and fix it by reviewing the source OLM file, conversion process, attachment size and health of the PST file.

This article discusses the reasons for attachment loss during the OLM to PST conversion process and provides some practical troubleshooting methods to recover or preserve them.

Why Users Need to Fix Attachment Loss During OLM to PST Conversion?

The attachments are often more important than the email message itself. Losing them can leave a successful mailbox conversion incomplete.

There are five common situations in which you need to fix attachment loss.

1. Losing Important Business Documents

Business mailboxes typically contain contracts, invoices, quotes, reports and project documents. The email may be readable after the conversion, but it has limited value if the attached PDF or Excel file is missing.

For instance, an accounting team that is switching from Mac to Windows may need old invoice attachments for financial records.

2. Mac Users: Outlook for Windows Is the New Choice

OLM files are used by Outlook for Mac, whereas Outlook for Windows usually works with PST files. During a platform migration, users need the full mailbox data to be migrated.

And a partial conversion, where messages but not attachments are transferred, means extra work and possibly users needing to access the old Mac several times.

3. Need Full Mailbox Backup of Users

Some users convert OLM files to PST for the purpose of keeping a local mailbox backup. As a backup it should have the entire email structure with the messages and attachments.

Since attachments are not included, the PST file cannot be regarded as an exact copy of the original mailbox.

4. Migration Fails With Large Attachments

Large ZIP archives, high-resolution images, presentations or video files in emails can cause problems during conversion.

The process can terminate unexpectedly, skip a large item, or create an incomplete PST file. Often this is only found when the original and converted mailbox are compared.

5. Incorrect Conversion Method Was Used

Not all migration processes deal with OLM data in the same way. Manual sync methods may rely on a mail server, Internet connection, mailbox limits, and Outlook configuration.

If there is an error during the transfer, attachments may not be synchronized or may not appear in the final PST file.

Method 1: Check Attachments in the Original Outlook for Mac Mailbox

Best for: Those who discover that a couple of attachments are missing in the converted emails.

Check the source mailbox before blaming the conversion process. This tells you if the attachment was there before conversion.

Steps

1. Open Outlook on your Mac computer.

2. Open the original mail folder.

3. Search for the email with the missing attachment from the PST file.

4. Open the message.

5. Verify that the attachment name exists.

6. Try opening or saving the attachment.

7. Repeat the test on a few of the affected emails.

If the attachment doesn’t open in Outlook for Mac, the source email may be corrupted or incomplete.

You should also compare the original email with the converted version. Please check the subject, sender, date and attachment name. This helps verify that you are seeing the same message.

Pros

• Simple, free troubleshooting method.

• Quickly finds issues in source mailboxes.

• Avoids unnecessary repeat conversions.

Cons

• Requires access to Outlook for Mac.

• Does not automatically fix broken attachments.

• Manually checking hundreds of emails takes time.

Method 2: Export a New OLM File From Outlook for Mac

Best for: Those who feel the initial OLM export was not complete.

Sometimes the problem is not the mailbox. The OLM file used in conversion might have been created incorrectly, interrupted during export, or copied incompletely.

You can try creating a new OLM file.

Steps

1. Launch Outlook for Mac

2. Check the mailbox and ensure that important attachments are present.

3. Begin the Outlook export.

4. Select the items in your mailbox to export.

5. Pick a safe local spot for the OLM file.

6. Ensure the export process is fully completed.

7. Don’t close Outlook or shut down the Mac during the export process.

8. Check the new OLM file size.

9. Use the new OLM file for the conversion process.

If you realize the new OLM file is significantly larger than the previous copy, then the earlier export might be incomplete.

Pros

• Makes a new copy of the source mailbox.

• Fixes issues with an incomplete OLM export.

• Please do not change the original mailbox data.

Cons

• Requires Outlook for Mac.

• Exporting large mailboxes can take a long time.

• It does not repair attachments that are already missing from the source mailbox.

Method 3: Transfer Mailbox Data Using IMAP or Exchange Account

Best for: Users with a small to medium mailbox who want to use an Outlook-based migration process.

Outlook for Windows does not have a simple option to open an OLM file directly and export to PST. Another choice is to sync the mailbox data using a supported email account.

The whole idea is that you would upload or sync your emails from Outlook for Mac and then access the same mailbox in Outlook for Windows.

Steps

1. Set up an Exchange or IMAP-supported account in Outlook for Mac

2. Create the necessary folders in the configured mailbox.

3. Copy the email you need from the local Mac mailbox to the synchronized account.

4. Wait for Outlook to fully synchronize.

5. Check email via webmail if available.

6. Make sure you can open their attachments.

7. Set up the same email account in Outlook for Windows.

8. Synchronize all mailbox folders and messages.

9. Re-check the attachments.

10. If you want a local copy of the PST, use the export options in Outlook to create a PST file.

Do not export the PST immediately after adding the account to Outlook for Windows. Large mailboxes may still fetch data in the background.

Pros

• Good for small mailbox migrations.

• Allows checking attachments during synchronization.

• Uses the standard email account synchronization.

Cons

• Requires a stable internet connection.

• Server storage and attachment size restrictions may apply.

• Synchronization can be slow with large mailboxes.

• Incorrect sync may have caused items to be missing.

• More checks might be needed on folder structure.

Method 4: Check Outlook &Amp; PST File Issues

Best for: Users whose attachments have been converted but will not open properly in Outlook

Sometimes the PST file contains attachments, but Outlook is not able to access or display the mailbox item properly.

In this case, check the Outlook profile and PST file.

Steps

1. Make a backup copy of the converted PST file.

2. Start Outlook for Windows.

3. Open or add the PST file.

4. Test e-mails from different folders.

5. Check small and large attachments.

6. Save the attachment to a local folder.

7. If possible, test the PST file in a different Outlook profile.

8. Use the Outlook Inbox Repair Tool if your PST file is corrupted.

9. Scan the PST file.

10. Now open the repaired file again and check the affected emails.

Always work on a copy of the PST file before starting the repair process.

Pros

• Helps if the target PST file is corrupted.

• Can fix some issues with Outlook data files.

• Separates conversion issues from issues with the display in Outlook.

Cons

• PST repair can’t recreate attachments that were never converted.

• Extreme corruption may not be fully returned.

• Large PST files may take more time to scan.

Method 5: Re-Convert OLM File in Smaller Batches

Best for: Users with a very large OLM file or who have experienced repeated conversion failures.

An OLM file this size could have years of email data and thousands of attachments. Doing all of it in one operation may increase the chances of interruptions or resource-related problems.

The mailbox can be divided into smaller sections for easier troubleshooting.

Steps

1. Verify the size of the source mailbox.

2. Locate big folders such as Inbox, Sent Items and Archive.

3. Where possible group data by year and mailbox folder.

4. Process one section at a time.

5. After each conversion, open the generated PST file.

6. Review emails that have known attachments.

7. Log any folder with missing attachments.

8. Reprocess the affected mailbox section only.

Instead of having to process a decade’s worth of archived email all at once, you can look at mailbox data one year at a time.

Pros

• Helps you spot problem emails faster.

• It reduces the amount of data that has to be processed at any one time.

• Useful for troubleshooting large OLM files

• This is faster if only one part of the mailbox is impacted.

Cons

• Needs more manual organization.

• Need to manage multiple PST Files.

• The exact batch options depend on the method of conversion.

Professional or Advanced Solution for OLM Attachment Problems

In case of manual methods with multiple attachment skipping, the most feasible way is the advanced OLM to PST conversion process.

Professional Softaken OLM to PST Converter software is programmed to read the internal mailbox structure and transfer data into a Windows-compatible Outlook data file. A capable tool should be able to process emails along with their attachments, rather than just the message body as the only important content.

This is particularly useful when working with large OLM files, archived mailboxes, nested folders and emails with different types of attachments.

If you have an important mailbox to process, try a small sample or preview option to test the software. Choose some emails that have attachments in formats such as PDF, DOCX, XLSX, ZIP, JPG, and others. After the conversion open the PST file and compare its messages with the source mailbox.

Don’t judge a conversion by the number of folders or emails. Attachment integrity is also important.

For business migrations, it makes sense to keep the original OLM file intact as well. If possible, always work with a duplicate copy. This provides you with a clean source file in case you want to run the conversion again with different settings.

Advantages of an OLM to PST Conversion Technique

If your main objective is to preserve attachments, search for features that solve migration problems:

• Attachment preservation: Keeps files attached to original email communications.

• Large OLM files supported: Handles years of emails and large attachments in mailboxes.

• Preserves the folder hierarchy: Inbox, Sent Items, Archive and custom folders.

• Batch Processing: Ease of handling multiple OLM files or sections of the mailbox.

• Email preview: Lets users see mailbox items before the final PST file is saved.

• Selective conversion: Lets you convert selected folders rather than converting the entire mailbox again.

Conclusion

If you lose attachments during an OLM to PST conversion, what should be a simple mailbox migration can quickly turn into a frustrating troubleshooting exercise. First, ensure the missing attachment is in the original Outlook for Mac mailbox.

If the source data is good, make a new OLM export and try the conversion again. IMAP or Exchange sync method might be the trick for smaller mailboxes. If the converted PST is not acting right, check Outlook and the PST file for potential data file issues.

For large or complex OLM mailboxes, you may need to use smaller conversion batches or a professional OLM to PST converter that preserves attachments and mailbox structure.

Regardless of the method you select, make sure you keep the original OLM file and check the resulting PST before deleting or discarding the Mac mailbox.