I'm unable to permanently delete an IMAP account under MacOS 10.12.2.
- Deleting the account from System Preferences > Internet Accounts removes it, the entry in Mail,and the related keychain item, but they all reappear after several seconds.
- Using Keychain Access to remove the related keychain item achieves the same frustrating result.
- Disabling iCloud Keychain allows removal of the offending account, but it returns when iCloud Keychain is reenabled.
- Repeatedly resetting iCloud Keychain according to Apple's instructions hasn't helped. I've disabled the security code option, then disabled iCloud keychain on all my devices following the instructions to reset and empty it, and then removed it using Keychain Access. Reenabling iCloud Keychain causes it to reappear.
It seems the problem centers around the removal of a single item from iCloud Keychain and none of the techniques my research has discovered work.