A list of Clearance levels, their order, and corresponding security

Alpha - Public Domain

Beta - Enlisted Personell Only are allowed

Gamma - At least a tier two when applicable, if not, the second rank of the division can see this

Private - No registered personell, aside from superiors (inquiring about these things), the sender, and the addressee may view these

Zeta - Only High Command may see.

Omega - Highest level of security. Only the Owner, Seconds-in-Command, and What would be 'Thirds-in-Command' may view.