Before you waste your time trying any of the methods suggested above, you need to know that they are either fundamentally flawed or completely dead.
Why the suggested methods don't work:
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The POP3 Import Method: This technique is no longer viable. In January 2026, Google officially killed the "Check mail from other accounts" POP3 fetching feature. You simply cannot use this method to import your iCloud emails into Gmail anymore.
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Drag-and-Drop via Desktop Clients: Trying to connect both accounts to a desktop app (like Apple Mail) and dragging folders over is incredibly clumsy. It frequently times out, crashes, and almost guarantees you will lose emails or permanently corrupt your folder hierarchy.
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Manual Forwarding: No one has the time to forward thousands of emails one by one. Furthermore, doing so ruins the original sender data and timestamps, turning your carefully organized archive into a useless mess.
Because all these workarounds are either dead protocols or far too risky, the SysTools IMAP Migration Tool for Mac is genuinely the only solution left that actually works.
It runs natively on macOS and creates a direct, secure bridge between Apple's servers and Gmail. It processes the transfer in bulk while keeping every single folder, attachment, timestamp, and read/unread status 100% intact.
If you want to do this right the first time without losing a single message, follow this exact walkthrough: Transfer Emails from iCloud to Gmail
Don't gamble with your data using outdated hacks. Stick to a dedicated, Mac-native IMAP migration.