Re:Google Users Locked Out After 15 Years' Use (2020)
by sufehmi on Monday February 28, 2022 @06:29PM
(#30506679)
POP3 always fail when you have so much emails: https://news.ycombinator.com/item?id=30485039
IMAP only download the index - everytime you click on an email, it'll then download it. When you have 150K emails, then you need to click on all that emails 150K times.
Then, if you've setup a new email account with another provider, you can connect using IMAP and copy your emails that way.
https://support.mozilla.org/en-US/kb/thunderbird-and-gmail