For a large Gmail mailbox, I’d avoid the Outlook IMAP sync method. It works, but it can take a long time to download everything, and if the connection drops or Outlook’s cache isn’t set to sync the full mailbox, the exported PST may not contain all of your emails.
I’ve had good results with the BitRecover Gmail to PST Converter. It connects directly to Gmail using modern authentication, exports large mailboxes to PST, preserves labels, attachments, and folder hierarchy, and supports selective backup using date filters.
One feature I found especially useful is its incremental export. After the initial backup, it exports only newly arrived emails instead of recreating the entire PST, which is a big advantage if you’re maintaining a long-term archive of a large Gmail mailbox.
