It was a few months ago, so I don't remember exactly, but I believe I followed the instructions that fastmail provided. If you say you didn't have this problem then I will try again.
Thanks for the answer
Thanks for the answer
Also, of course, note that if you have a mail message under two Gmail labels, and use IMAP to copy your folders, you'll probably end up with two copies of that message.
Migrating out of Gmail, FWIW, is still a pain because they are so nonstandard now.
But I never had an issue with the dates on the emails.