I'm preparing to migrate an old email archive containing several thousand EML files, and doing everything manually just isn't realistic. Besides wanting to convert an EML file to PDF for record-keeping, I also need to move the entire collection into Outlook and Office 365 without losing folder structure or message data.

During my research, I came across MacSonik EML Converter, and what caught my attention was its bulk processing capability. Instead of selecting emails one by one, it allows multiple EML files to be added and converted in a single operation, which sounds like a huge time saver for larger archives.

Another feature I found interesting is the Date Range Filter. Rather than migrating every email ever received, it lets you export messages from only a specific period. That's especially useful if you're archiving old records while keeping recent emails separate.

The software also claims to support very large EML files without imposing size restrictions, something many tools struggle with. To keep the exported data organized, it includes options like custom folder naming and naming conventions for the output files.

One feature I didn't expect was automatic duplicate email removal. It can detect duplicates based on fields like Mail, Body, From, and To, which should help reduce unnecessary storage after migration.

Has anyone here migrated a mailbox with 20,000+ EML files? I'm curious whether bulk conversion maintained the original email structure and whether the filtering options actually reduced migration time in real-world use.