Together with an account at HPC2N you will also get an email address. However, you cannot log in to read it at HPC2N so you will need to set up a .forward file pointing to your home/other email. This file will be used by HPC2N to determine where to send you any information.
The .forward file should only contain the email address you wish your mail sent to. A simple way to create this file is (after logging in to akka or other HPC2N cluster):
$ echo email@example.com > ~/Public/.forward
When you account is created the .forward file is created with the email address you entered on the account application form and you only need to change it if that email address changes.
Note that HPC2N requires you to give a working email address, and that your account may be disabled if mail sent to it starts bouncing.