How to backup gmail using another gmail account?

1, Create a backup email account, for example backup@gmail.com

2, login backup@gmail.com and click "Settings"

3, Click "Accounts", you will see "Get mail from other accounts:
(Download mail using POP3)"

4, click "Add a mail account you own"

5, a popup window will be opened

6, enter your gmail address

7, enter your pop server info
If you use gmail, your user name is full email address
pop server : pop.gmail.com
port :995
check checkbox: Always use a secure connection (SSL) when retrieving mail.

8, click save

That is it.

You may backup other email using gmail too.