After having upgraded to Leopard 10.5.2 and enabling IMAP support through Mail.app, I have had a problem with a new label being consistently generated on my gmail account. No matter how many times I deleted it from gmail, Mail.app would happily recreate it every time I launched it.
Tonight, I was able to figure out how to make this go away. I dont know if it is because of the order of steps that I followed. This worked for me; your mileage may vary.
- Open Mail.app and visit your account preferences (CMD-,) and select the Mailbox Behaviors tab for your gmail account.
- Uncheck the field that says 'Store notes in Inbox'
- Quit Mail.app. Don't use the red Close button, but quit completely with CMD-Q.
- Go to gmail.com and delete the Apple Mail To Do label from the Settings | Labels tab.
- Restart Mail.app and refresh gmail to notice that the pesky label is no longer there.
I hope that this helps other people that want to get rid of this pesky label as well. Enjoy.