If you are a citizen or resident of new zealand, you could possibly sue them.
They claim that their warning is sufficient but you could argue that one mass generated email does not constitute efficient.
If you are not a citizen or resident of New Zealand, you are out of luck.
Since cryptopia is a nz company, you would have to get an international lawyer that would most likely cost you more than what you deposited.
Actually, just suing them normally would probably cost you more than also.

It totally sucks, but there is probably nothing you can do.
The best way to cope with your loss is to make a strategy to make back what you lost.
Research some different strategies and get active in making up for your losses.