How to fix incorrect dates in emails in Outlook after a migration

We encountered a situation where an email displayed one date in the Message List Area in Outlook but a different date in the Preview Pane. This issue affected nearly 20,000 emails. The screenshot below provides a visual reference to illustrate what we observed.

How did this happen:

Sometimes, when emails from an email provider (e.g., iCloud) are moved to another platform (e.g., Office 365) using Apple Mail, the emails can become ‘corrupted’ in this manner.

Solution:

• Set Up Thunderbird:
  • Install the latest Thunderbird email client and load the Office 365 account.
  • Use the “Owl for Exchange” add-in to log in to the Office 365 account. This add-in is free for a few months upon installation. This will properly load up all the Outlook folders.
• Export Affected Emails:
  • On Thunderbird, select and drag all affected emails into a folder on your Windows machine.
  • To make the process manageable, batch the emails into folders of approximately 2,000 each in Thunderbird.
  • The drag-and-drop action will create .EML files. Be patient, as this process may take some time.
  • Random sample some EML files and check to make sure they’re displaying correct. Use Outlook to view the EMLs.
• Convert EML to PST:
  • Use a commercial tool like “Kernel for EML to PST Converter” by Kernel Data Recovery (we tried that and it works, we don’t have any relationship with them, please use at your own risk). Start with the demo version to evaluate the tool.
  • Convert the .EML files to .PST (or .MSG, but PST is recommended).
• Import PST into Outlook:
  • Open the PST files in Outlook (classic version) and drag and drop the folders into your Outlook account.
  • The email dates should now be corrected. Allow Outlook to sync.

Explanation:

In Outlook (new), the dates on affected emails were incorrect. However, in Outlook (classic), the same emails display two different dates— one in the Message List and another in the Preview Pane. The date in the Preview Pane is the correct one.

This discrepancy (probably) occurs because Apple Mail uses the open-standard .EML format, while Outlook (classic) uses Microsoft’s proprietary .MSG format. Outlook (new) has reverted to using .EML as its format, leading to these inconsistencies.

We discovered that opening the affected .EML files in Outlook (classic) and then moving them into a folder via the menu corrected the dates. However, given the volume of emails, manually processing each email was impractical. This led us to the above solution involving batch conversion.

Further Observations:

• Outlook does not provide a built-in way to convert .EML files to .MSG. (There are ways to do it in a low volume solution.)

• Microsoft Support was unable to assist, stating that the email transfer was done outside Outlook (in Apple Mail) and was therefore unsupported.

• We believe this issue is a Microsoft bug, as Outlook fails to natively and properly convert .EML files (originating from Apple Mail) to .MSG, leading to this problem.

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