1. Login to Register and go to Nexus options:
https://register.it.ox.ac.uk/self/nexus
(Or you can click the link on the left menu)
2. Select Email forwarding address settings
3. Enter a valid email address in the box (one address per line)
And decide whether you want to keep a copy in your Nexus mailbox.
4. Click Submit
All emails will now be forwarded to the email address you provided.