I had the need to retrieve mails from one Google App account to another Google App account over POP. Like this you can actually “swap” from one primary domain to another primary domain (since Google does not allow it to be exchanged you need to create a new account and do all the needed steps as outlined in their document called “Swap primary domains“).
Since this is going from one Google App account to another I thought it would be very easy to do so. But as it turned out it wasn’t. Mainly because there is almost no documentation out there. The process itself is quite simple, all you have to do is to go to the “Settings” page within your account. Then go to “Accounts” and under “Get mail from other accounts” you add your other eMail account.
But the problem is that, even this is from Google to Google account, the wizard does not configure correctly. By default you might get filled in information like:
User: yourname
Mail Server: mail.domain.com
Port: 110
But to be able to retrieve mails over POP from another Google App account you will need the following settings:
User: name@domain.com
Mail Server: pop.gmail.com
Port: 995
Figuring out this setting took some valuable time. Hope someone else benefits from it.