Security
Guardrails you can't argue with.
The point of Mailstack is that its most important rules live in the schema and the function signatures — not in a policy document, and not in a prompt.
Your data is yours, on your plane
Mailstack owns the mail server, the reputation planes and the suppression ledger — you're not renting a scope into a mailbox someone else can revoke.
Accounts, roles and revocable sessions
One account, many people, each with their own login and a role the owner controls. Sessions are rows you can kill; a leaked database exposes only their hashes.
Authentication and encryption by default
SPF, DKIM and DMARC alignment on every domain, TLS on the wire, and one-click unsubscribe where the rules require it.
Suppression is global and permanent
An opt-out silences every campaign from every list, forever. There is deliberately no way to un-suppress by accident.
Signed links carry their purpose
A reset link cannot be replayed as a verification link — the purpose is inside the signature, and reset links are single-use.
Agents are limited by shape, not by prompt
The functions an agent can call take no recipient it shouldn't have. The limits a model can read are the limits it truly has.