Does Microsoft 365 archive email automatically?

It's one of the most reasonable assumptions in IT: "We pay Microsoft for email — surely they keep everything, right?" Sort of. Sometimes. Depending on your license tier and on settings someone would have had to configure. The honest answer to "does Microsoft 365 archive email automatically?" — or Office 365, as many still ask — is: not in the way most people mean when they ask.

What people usually mean is: "If an email existed in our company, can we find it again years later, even if someone deleted it, even if the employee left?" Let's walk through what the built-in features actually do, measured against that expectation.

What happens to a deleted email in a default tenant

Out of the box — no retention policies, no holds — a deleted email in Microsoft 365 has a surprisingly short life:

That's the baseline. Everything else depends on features someone has to know about, license, and switch on. Here's what each one really does.

The "Online Archive" — a bigger attic, not an archive

Exchange Online's In-Place Archive (the "Online Archive" folder users see in Outlook) sounds exactly like what you want. It isn't. It's a storage feature: a second mailbox that older mail gets moved into so the primary mailbox stays fast and under quota.

• Users can still delete anything from it, any time.
• It only holds what a policy moved there — the default auto-archive setting moves mail older than two years once the archive is enabled. Deleted mail never arrives at all.
• It's tied to the user's account: account gone, archive gone.

Think of it as a bigger attic for the same house. When the house burns down, the attic goes with it.

Retention policies — powerful, but not automatic

Microsoft Purview retention policies are the real preservation mechanism: they can keep copies of deleted and edited mail in a hidden folder for a defined period, org-wide or per mailbox. Configured correctly, they genuinely preserve messages. The catches:

• Nothing is on by default. A fresh tenant preserves nothing. Someone has to design and enable the policies.
• Licensing matters. Meaningful retention setups typically require Exchange Online Plan 2 or E3/E5-class licenses — many small businesses are on Business Basic/Standard.
• Retrieval is an admin exercise. Preserved mail lives in Recoverable Items and comes back out via eDiscovery/content search — a specialist workflow, not something a bookkeeper does to find one invoice.
• Policies can be changed. An admin can shorten or remove a policy later (unless you add a Preservation Lock, which very few SMBs do — partly because it's genuinely irreversible).

We compare this option against a dedicated archive in detail here: Microsoft 365 retention policies vs. a dedicated email archive.

Litigation hold — the special-purpose tool

Litigation hold freezes a mailbox's content, including deletions — designed for legal proceedings, requires Exchange Online Plan 2, applied per mailbox. It works, but using permanent litigation holds on every mailbox as a poor man's archive means running your whole company in "we're being sued" mode, with the same eDiscovery-only retrieval story.

So — are you covered?

A quick self-test. You're reasonably covered by built-in tools if all of these are true:

1. Every mailbox has an E3/E5 or Exchange Plan 2 license,
2. someone deliberately configured org-wide retention policies (and documented them),
3. your offboarding process reliably produces inactive mailboxes, and
4. you're comfortable that finding old mail always goes through an admin running eDiscovery.

For most small and mid-sized tenants, at least one of those is false — usually all four. That's not a Microsoft flaw; preservation simply isn't what the defaults are for.

That last part is what a dedicated archive adds on top: mailvault365 connects to your tenant with read-only access and preserves every email automatically as it arrives — regardless of license tier, deletions, or departures — with search that anyone can use. Setup takes about five minutes, and the built-in Microsoft features keep doing what they're actually good at.