One issue I think is easy to overlook during a mailbox move is duplicate data. If an employee has archived messages, local PST files, and an existing destination mailbox, there can be several copies of the same email. Moving everything without checking for duplicates could leave the new mailbox unnecessarily cluttered.

I was looking into the SysInfo Email Migration Softwareand noticed that duplicate removal is included among its migration-related options. The software supports several source types, including PST/OST, IMAP/POP3, Microsoft 365, GoDaddy Office-based accounts, and Hotmail/Outlook.

I also like the idea of combining duplicate handling with other filters. For example, an administrator may only need emails from a specific period rather than an entire mailbox history. Date Range, Item Type, attachment-related filters, read/unread status, and unwanted sender options can help narrow the migration before data reaches the destination.

This becomes particularly relevant during an email migration involving multiple accounts. If dozens of mailboxes are being moved, manually checking every destination for repeated messages would take considerable time. Batch processing and migration reports can make the overall process easier to monitor.

Another feature worth checking is whether previously migrated data can be skipped. This can be useful when a migration needs to be performed in stages or when a failed task has to be restarted without unnecessarily processing the same data again.

For very large projects, businesses may consider email migration services to handle planning and execution. However, organizations with an experienced IT team may prefer to manage the process internally and use software with filtering and reporting capabilities.

How do you normally deal with duplicate emails during a migration? Do you remove them before the transfer, let the migration software handle them, or clean up the destination afterward?