If you want to move IMAP data into Zoho Mail for a large mailbox, start by enabling IMAP access in your source email account. Then, log in to your Zoho Mail account and go to Settings > Mail Accounts > Add External Account. Choose IMAP migration and enter your source server details, including hostname, port, username, and password. For large mailboxes, it's best to use MSOutlookHelp IMAP Wizard tool, which allows bulk transfer with better stability and progress tracking. You can also migrate data in batches using date filters to avoid server timeouts. Ensure a stable internet connection throughout the process. After migration, verify folders and emails for accuracy.