Oh, shiny new Mavericks. Seems okay. Then, you use Mail.app with your Gmail account. You had gone through the list of tweaks that were necessary to make it “just work” up until yesterday. Now, you go about your business dragging messages to their resting places, have a look at what’s in another folder for a moment, and return to your inbox – to find yourself blinking for because there are all those messages you just moved. Hm, some wonky sync, and you do it again. Upon return to your inbox the blink becomes a twitch of annoyance, but a google search provides an irritant balm in the form a TidBits article by Joe Kissell, “Mail in Mavericks Changes the Gmail Equation.” Basically you must expose the All Mail tag in your Gmail account to IMAP (Gmail:Settings:Labels>>All Mail>>Show in IMAP). I share his sentiment:

I find it particularly upsetting that Mail doesn’t tell you about the need to enable All Mail. Mail could pop up a little message saying, “Hey there! I noticed that you have a Gmail account and I’m not seeing All Mail. That’s going to be a problem from now on; here’s how you fix it.” But this is something you just have to work out for yourself — a major architectural change that isn’t even mentioned when you choose Help > What’s New in Mail?, let alone addressed in a helpful error message.

NOTE:  This is not a nice solution and will cause Mail to freak for quite some time, but it settles itself down … eventually … I am told. All your folders will seem to be empty. Have a look at Activity under Window to see all the unnecessary.

UPDATE: This situation has led me to Airmail, and I’m really quite impressed. The beta is free and the full app is in the store for just $1.99. I may just stay with this even when Apple gets around to bandaging themselves.