The 4 principles that decide what Purview actually keeps

Most organisations end up with multiple retention policies. An org-wide policy that retains everything for 7 years. A department-specific policy for Finance with 10-year retention. A cleanup policy that deletes stale Teams chats after 1 year. A retention label on a specific contract that must never be deleted.

What happens when a single item is covered by three of those at once? The answer is not obvious, and getting it wrong means content is either deleted too early (compliance risk) or kept too long (storage cost and data exposure).

Microsoft resolves these conflicts using four principles, applied in order. They are predictable once you know them, but most admins learn them the hard way during an audit.

If any policy or label says retain, the content is retained. It does not matter if another policy says delete. Retain always wins.

Example: Policy A says retain SharePoint content for 7 years. Policy B says delete SharePoint content after 1 year. A document covered by both policies is retained for 7 years. Policy B's delete instruction is overridden.

This is the most important principle because it protects you from accidental data loss. You can safely add a delete-only cleanup policy without worrying about it overriding your retention policies. The retain action always takes priority.

The practical catch: this means delete-only policies only take effect on content that is not covered by any retain policy. If you want to clean up stale content, make sure you understand which locations already have a retain policy applied.

When multiple retain policies cover the same content, the one with the longest retention period wins.

Example: An org-wide policy retains Exchange mailboxes for 7 years. A Finance-specific policy retains the same mailboxes for 10 years. A Finance employee's email is retained for 10 years.

Retain-only policies (no deletion after retention) are treated as having an indefinite period. They always win over retain-then-delete policies because indefinite is longer than any fixed period.

What this means in practice: you do not need to worry about policy order or priority settings. There is no priority number. The system simply keeps the longest period. This makes it safe to layer policies - a department policy cannot accidentally shorten the org-wide retention.

This is the principle most people miss. It applies in two ways:

Retention labels beat retention policies. A retention label applied to a specific item is explicit - someone or something deliberately tagged that item. A retention policy is implicit - it applies to a whole location. When they conflict on what happens at the end of retention (delete or keep), the label wins.

Example: An org-wide policy says retain SharePoint content for 5 years then delete. A retention label on a specific contract says retain for 5 years then keep permanently. Both have a 5-year retention period, so Principle 2 does not break the tie. Principle 3 does: the label's explicit instruction to keep permanently wins over the policy's implicit delete.

Scoped policies beat org-wide policies. A policy targeted to specific users, sites, or groups via an adaptive scope is more explicit than one applied to all users. When two policies have the same action and period, the scoped one wins.

Note that Principles 1 and 2 are checked first. Principle 3 only breaks ties that those two cannot resolve. In most real-world setups, the period difference alone is enough.

When only delete-only policies apply to content (no retain policy covers it), the shortest deletion period wins. Content is deleted as soon as the shortest period expires.

Example: Policy A says delete Teams chats after 1 year. Policy B says delete Teams chats after 3 years. Content is deleted after 1 year.

This principle only matters when no retain policy covers the content. If any retain policy applies, Principle 1 kicks in first and the delete policies are overridden entirely.

Why shortest wins: Microsoft designed this for safety. If someone has decided content should be deleted after 1 year, a broader 3-year policy should not keep it around longer than intended. Deletion is treated as a deliberate compliance action.

Open the Retention Policy Builder and load your policies. The What If tab lets you test specific scenarios against all four principles. Try these:

1. Pick a content area covered by multiple policies and check what happens when a user deletes it.
2. Toggle the retention label checkbox to see how a label changes the outcome.
3. Load the "Label blocks policy deletion" preset to see Principle 3 in action.

If you find overlapping policies with conflicting actions, that is not necessarily wrong - the principles will resolve it. But you should be able to explain why the outcome is what it is. If you cannot, simplify your policy set.

The most common gap: organisations have retain policies for Exchange and SharePoint but forget Teams chats and Copilot interactions. Use the Coverage tab to spot these.