I managed it on my Lumia 640 / WP10, similar set up with my domain in the address but 1&1.co.uk servers. Of course that was all a long time ago, so I can't remember exactly what I did, but I don't recall having any trouble and it can definitely be done. I used IMAP rather than POP, but that shouldn't make any difference.
It's always worth double checking that you've spelt the server names correctly and that you're using the exact format required for username and password
I managed it on my Lumia 640 / WP10, similar set up with my domain in the address but 1&1.co.uk servers. Of course that was all a long time ago, so I can't remember exactly what I did, but I don't recall having any trouble and it can definitely be done. I used IMAP rather than POP, but that shouldn't make any difference.
It's always worth double checking that you've spelt the server names correctly and that you're using the exact format required for username and password