Hey everyone, I recently had to move a client's mailbox from an IMAP server (Gmail, Zoho, GoDaddy, Rediffmail, etc.) over to Microsoft 365, and I wanted to share what worked for me in case anyone else is stuck on this.
Manually exporting/importing PST files or relying on the built-in Office 365 migration options can get messy fast — especially once you factor in nested folders, read/unread flags, attachments, and duplicate emails. I tried a couple of free utilities first and ended up with broken folder hierarchies and missing attachments, which was a headache to fix afterward.
What finally worked without any data loss was a dedicated DRS Softech IMAP to Office 365 Migration Tool. It handled the full mailbox — emails, folder structure, attachments, and even filters like date range — in one batch process, and it also supports migrating multiple IMAP accounts to Office 365 at once, which saved a ton of time for bulk migrations.

A few things I'd suggest checking before picking any tool:

• Does it preserve folder hierarchy and metadata (read/unread, flagged, etc.)?
• Can it handle bulk/multiple mailbox migrations?
• Does it support incremental migration (in case the process gets interrupted)?
• Is there a free trial to test with a small batch first?