I abandonded WXC residential 2 years ago, their 30/10 fibre got left behind by the market.
2 years later, my old @xnet.co.nz email address is still working - don't use it anymore, but just logged in on webmail and confirmed it's still live.
I cant see any option to set up forwarding in the webmail interface.
The webmail software they use is called Roundcube Webmail - which is free under GNU, so I'm guessing it's set to auto and will just keep going.
Gmail has ability to set up option to check emails from other accounts.
So maybe not such an issue if you can set Gmail up and buy time to get everything switched over.