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Title
Investigating Missing Mail Items After Migration -
Description
After a mailbox migration, the customer reports missing mail items. In this case, a few Gb of data appears to be missing from the target mailbox, despite no warnings or errors being logged during the migration task. -
Cause
Possible Causes:
- Differences in mailbox folder structure between source and target
- Aggressive archiving policies in the target tenant
- Items filtered out during migration due to size or type restrictions
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Resolution
Gather detailed mailbox statistics: Run the following PowerShell commands on both source and target environments:# Source Mailbox Get-Mailbox <source_email> | Get-MailboxFolderStatistics | Select-Object Identity,ItemsInFolderAndSubfolders,FolderAndSubfolderSize | Export-Csv -Path "C:\temp\Source_output.csv" -NoTypeInformation # Target Mailbox Get-Mailbox <target_email> | Get-MailboxFolderStatistics | Select-Object Identity,ItemsInFolderAndSubfolders,FolderAndSubfolderSize | Export-Csv -Path "C:\temp\Target_output.csv" -NoTypeInformation
- Analyze the resulting CSV files:
- Compare folder structures, item counts, and sizes between source and target
- Identify any significant discrepancies
- Check archive folders:
- Verify if the target tenant has a more aggressive archive policy
- Examine the archive mailbox in the target environment for the potentially missing items
- Review migration logs:
- Check for any filtered items due to size or type restrictions
- Investigate specific discrepancies:
- If particular folders show significant differences, examine their contents more closely
- Analyze the resulting CSV files: