Gmail, IMAP, and “Account Exceeded Bandwidth Limits”

Apple Mail is failing to fetch mail from Gmail, with the following error:


Googling this error message shows lots of other people running into the same problem. Some bandwidth limit on Google's side is cutting me off. When this happens, I'm put in a penalty box and not allowed to connect via IMAP for some period of time.

I'm not using mail excessively. I don't get a lot of big messages; I do get a lot of spam but there's not much I can do about that.

Other users have complained to Google and gotten nowhere. I'm not paying for this service so it's not like I can call a customer support line and threaten to quit. What can I do?