IMAP to Office 365 migration tool for large migration

10 Jul 26 9:55 am

IMAP to Office 365 migration tool for large migration

Hi everyone, I'm looking into options for migrating a fairly large IMAP mailbox (years of emails, multiple folders, lots of attachments) to Office 365 and wanted to see what others have used for bigger transfers like this.

I came across the DRS Softech IMAP to Office 365 Migration Tool, and a few things about it seem relevant specifically for large-scale migrations:

Skip Previously Migrated Items — useful if a large migration gets interrupted, since you can resume without duplicating everything that's already transferred
Remove Duplicate Emails (based on To, From, Subject, Bcc, Body) — helps keep things clean when dealing with a big mailbox
Migrate or backup emails without attachments — an option if you want to reduce data size during a large transfer and handle attachments separately
Mail filter option (date, subject, sender) — lets you break a large migration into smaller, targeted batches instead of moving everything at once
Log and temp path settings — lets you track migration activity, which is handy for monitoring a long-running job

It also preserves attachments, inline images, email formatting, and folder hierarchy during migration, and supports bulk migration via CSV if you're moving more than one account.
The free demo version only migrates the first 100 emails per folder, so it's worth testing on a sample folder first to check formatting and folder structure before running a full large mailbox migration on the licensed version.