Back up Gmail to a local drive

Although many people are comfortable keeping data only in the cloud,
I'm not one of them. I'm sure that Google backs up regularly, and keeps
my data on multiple servers. But I still feel better keeping a local
copy of my own. 



But how do you do that?


The obvious solution is to use POP or IMAP to access your mail
through a local mail client--such as Outlook. But that won't back up all