Moving Office 365 Mailboxes to IMAP Servers - What’s the Best Approach

I’ve recently been looking into scenarios where organizations need to move mailboxes from Microsoft 365 to IMAP based email servers, and I noticed this is still a common requirement in many migrations.

In most cases, the challenge is not just moving emails, but making sure everything like folder structure, old emails, and user data stays intact without creating too much disruption for users.

From what I’ve seen, doing this manually can get very complex, especially when there are multiple mailboxes or large data volumes involved. That’s where migration tools usually come into the picture.

Most tools simplify things by handling:

1. Secure connection to Microsoft 365 accounts

2. Bulk mailbox migration

3. Preserving folder hierarchy

4. Reducing downtime during the move

5. Avoiding duplicate data issues

One thing I’ve noticed is that running a small pilot migration first always helps. It gives a clear idea of how the actual migration will behave before moving all users.

Has anyone here worked on Office 365 to IMAP migration at scale? Would be good to know what approaches or tools worked best in your case and what challenges you faced during the process.