To migrate IMAP emails to Office 365 without losing attachments, use a reliable migration tool that transfers complete mailbox data while preserving attachments and the original folder structure. First, connect your IMAP account and Microsoft 365 account, then select the required folders and configure the migration options. SysInfo IMAP Backup Tool can help simplify this process by supporting batch migration, folder mapping, advanced filters, and duplicate removal. It is designed to preserve important email data, including attachments, metadata, timestamps, read/unread status, and folder hierarchy during migration. The tool also supports incremental synchronization, which can help transfer newly added emails without repeatedly migrating existing data. Users can process multiple IMAP accounts through CSV-based batch migration, making it useful for organizations handling several mailboxes. Its local processing approach helps keep mailbox information private during the migration. With folder mapping and progress tracking, users can organize the migration more efficiently and move IMAP emails to Office 365 while retaining essential mailbox data and attachments.

The safest way is to use an IMAP migration tool or Microsoft’s built-in migration process. It copies emails and their attachments directly to Office 365. Before starting, take a backup and test a small mailbox first to make sure everything transfers correctly.