Mac Mail: Check for new messages doesn't work

Hi,

In Mac Mail the setting at "Preferences -> Check For New Messages" I have set for manual and yet Mail still fetches emails when I haven't asked it too. I previously had this setting set to check for messages every hour but it ignored that setting too so I set it to manual but this setting is ignored. Ideally I'd like to check mail every four hours but there isn't a setting for that.

I'm running Lion and have IMAP email accounts.

Any idea how I can get Mac Mail not to ignore my Check For New Messages setting?

Thanks!