Data mining will not exist in a decentralized email system. Both account and server reside only on the user devices. Proemtheus will not be the holder of the email account nor have a backdoor.
Accounts exist INDEPENDENT.
As we mentioned in a previous post we intend to construct Proemtheus in such a way that the accounts function with or without our company.

In regards to spam well nobody has eliminated spam completely: filtration, filtration and filtration.
For the first 2-3 years we plan to rely on common techniques currently in place. Your account will be as spam free as any other account.
We have also in plan some new filtering options and inter-user collaboration for reporting spam.
Equally important will be the users from the community, developers - auditors - reviewers etc, that will be token rewarded for reporting.