Mailbox governance is the set of rules, permissions, and administrative controls that decide who can read, send, archive, forward, delegate, or delete email content. It covers not just user passwords, but also shared mailboxes, inbox delegation, retention rules, audit logs, and access reviews. In security terms, it answers a simple question: who is allowed to handle a message, and under what conditions?
It matters because email often carries sensitive business, legal, or customer data. If mailbox governance is weak, an attacker or insider may exploit excessive permissions, hijacked accounts, permissive forwarding rules, or poorly managed shared mailboxes to move quietly through an organization. Strong governance reduces that risk by limiting access to need-to-know users, separating sensitive mail from routine traffic, logging administrative actions, and regularly reviewing mailbox ownership and delegation. In practice, it is one of the main defenses against email-based data exposure and misuse.