Holy mail

"Holy Mail"! That's an interesting phrase. Could you please provide more context or clarify what you mean by "Holy Mail"? Are you referring to:

1. A type of mail or package that is considered sacred or of great importance?
2. A metaphorical or figurative sense of "mail" that is related to spirituality or the divine?
3. Something entirely different?

I'm here to help and provide assistance, so please feel free to share more about what you mean by "Holy Mail"!