To backup IMAP emails in MBOX format, you can use the MailConverterTools IMAP Migration Tool. First, log in to your IMAP account through the software. The tool will display all mailbox folders, allowing you to preview emails, contacts, calendars, and tasks. Next, choose MBOX as the export format and apply optional features, like filtering emails by date or removing duplicates. Finally, start the backup process. The IMAP Migration Tool will save all your IMAP emails in MBOX format while maintaining the original folder structure and complete data integrity.