Our company is upgrading from a legacy IMAP email hosting environment to Microsoft 365, and I'm responsible for planning the migration. We have several hundred active mailboxes, including shared accounts that multiple departments access every day. The biggest concern isn't moving the emails—it's making sure everything remains organized after the migration. We need folder hierarchy, read/unread status, attachments, and timestamps to remain exactly as they are today. Since employees will continue using their mailboxes until the migration weekend, incremental synchronization is also an important requirement.

I've been evaluating different solutions and recently started testing an IMAP Migration Tool that supports batch account processing, mailbox preview, advanced filtering, and migration reporting. Those features seem useful because manually handling hundreds of accounts would take far too long. We're also considering running several pilot migrations to validate authentication, mailbox mapping, and overall migration speed before touching production users. Another requirement is detailed reporting so we can verify every mailbox after completion and quickly identify any skipped items.

For teams that recently Migrate IMAP to Office 365, how did you manage the final migration window? Did you stop user access before synchronization, or allow employees to continue working until the last stage? I'm also curious how you validated large mailboxes and whether there were any unexpected issues with authentication, folder permissions, or duplicate emails after the migration was complete.

While comparing different migration utilities online, I also found the DRS Softech IMAP to Office 365 Migration Tool listed among enterprise solutions. The documentation mentions incremental migration, batch processing, Office 365 connectivity, and multiple export options, which seem relevant for larger deployments. Before making any recommendation internally, I'd appreciate hearing about real-world experiences, common challenges, and any best practices that helped make enterprise IMAP migrations successful.