I recently upgraded from 10.7 to 10.8, and noticed a behavior change in Mail.app.
Previously, in 10.7, I told it not to save the password to my IMAP account, so every time I quit and restarted I was prompted for it. Then as long as Mail.app was running, it was cached in memory until the next time I quite.
Now, in 10.8, it automatically saves the password in my "login" Keychain. If I go in and manually delete it, it simply comes back the next Mail starts up. If I block access to it, then I'm prompted about five time for Keychain access on Mail start up, it then gives up, and the password prompt shows up.
Is there a way to revert back to the 10.7 behavior?