E-mail is never used to convey secret or private keys, components or shares, even encrypted, unless the key was already encrypted inside an SCD, because the value sits in memory before encryption and after decryption and corporate mail systems let support staff recover clear text; SMS, fax and telephone are likewise banned for clear-text key values.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.