can this mailbox be attached to an existing metal mailbox pole and if so, how?

Hello, it will depend on whether or not your existing mailbox post has a mounting plate and what types of mounting hole patterns it has. The Cambridge mailbox has a 4x10 inch and 5.1x5.1 inch square mounting hole patter pre-drilled into the bottom of the mailbox. Feel free to email support@architecturalmailboxes.com with a photo of your existing post if you have further questions!