Duplicate emails usually show up after merging EML backups because the same mailbox data gets exported more than once, or different folders contain overlapping messages. When everything is combined the system doesn’t recognize duplicates automatically since EML files are just standalone email records.
If the collection is small, you can try a manual cleanup:
- Import EML files into Thunderbird or Windows Mail
- Sort emails by subject, sender, and date
- Remove obvious repeated entries one by one
But once folders are large, this method becomes messy. Some duplicates also differ slightly in headers, so they are hard to spot manually.
In cases like this, I’ve seen people use
GainTools EML Duplicate Remover. It scans multiple EML/EMLX files together and compares email attributes to filter identical messages, then creates a cleaned output without touching the original set.
One thing I’d suggest is always keeping the original merged folder untouched before running any cleanup, just in case you need to cross-check later.
