When legal or compliance says "put a litigation hold on these mailboxes" — or when a user's archive is about to hit its ceiling — the reflex in most tenants is to upgrade those users to E3. At $39 per user per month on Microsoft's current list, that's a $468-per-seat-per-year reflex for a need that costs $3.
Microsoft's own licensing docs draw a much narrower line than most admins assume. To place an Exchange Online mailbox on litigation hold, Microsoft Learn requires either Exchange Online Plan 2 — or Exchange Online Plan 1 plus the Exchange Online Archiving add-on. That same combination unlocks auto-expanding archive storage up to 1.5 TB per user. The add-on is $3.00 per user per month, paid yearly, and it stacks onto the user's existing license — including the mail entitlement in Business Standard.
So the 15 or 20 people who need hold or big-archive coverage — executives, legal, finance — don't need E3's Intune, Defender, and Windows Enterprise riding along at $39 a head. They need a $3 line item.
The math
| Measure | Amount |
|---|---|
| Exchange Online Archiving add-on | $3/user/mo, paid yearly |
| Microsoft 365 E3 | $39/user/mo, paid yearly (annual commitment) |
| Litigation hold entitlement | Exchange Online Plan 2 or Plan 1 + Archiving add-on |
| Auto-expanding archive ceiling | 1.5 TB per user (either route) |
| 20 hold-needed users via E3 upgrades | $9,360/year |
| Same 20 via the $3 add-on | $720/year |
The decision rule, per user
- Needs hold/archive and already uses E3's Intune, Defender, or Windows Enterprise → keep E3.
- Needs hold/archive and nothing else from E3 → $3 add-on.
- Hold coverage needed for 100+ users with no E3 usage → the add-on still wins at list (100 users: $3,600/yr vs $46,800/yr) — but get a CSP quote; real pricing can change the shape of this.
- The compliance program needs auto-labeling, eDiscovery Premium, or insider risk → those are E5-side; don't let a $3 saving become a coverage gap.
Step by step
- Buy the add-on. Microsoft 365 admin center → Billing → Purchase services → search "Exchange Online Archiving" → buy one seat per hold/archive user on annual commitment ($3/user/mo).
- Assign it. Users → select the users → Licenses and apps → check the Exchange Online Archiving add-on. It stacks onto their existing license; nothing else changes.
- Enable the archive mailbox. Exchange admin center → Recipients → Mailboxes → select the user → Others → Manage mailbox archive → enable. Or in Exchange Online PowerShell: Enable-Mailbox -Identity user@domain.com -Archive.
- Turn on auto-expanding. Per user: Enable-Mailbox -Identity user@domain.com -AutoExpandingArchive. Whole organization: Set-OrganizationConfig -AutoExpandingArchive. Verify with Get-Mailbox user@domain.com | Format-List AutoExpandingArchiveEnabled.
- Place the litigation hold. Microsoft Purview compliance portal → Data lifecycle management → Exchange (legacy) → create the hold on the mailboxes. (Or the Exchange admin center for mailbox-level hold.)
- Keep the license on. Holds and archives need the license continuously — audit license assignments at renewal before cleaning up "unused" seats.
20 hold-needed users upgraded to E3: $8,640/year back ($9,360 − $720) — same hold, same 1.5 TB archive ceiling, no E3 features nobody asked for.
One purchase, license assignments, two PowerShell cmdlets.
Prices verified October 23, 2026: Exchange Online Archiving ($3.00/user/month, paid yearly) and Microsoft 365 E3 ($39.00/user/month, paid yearly, annual commitment) on Microsoft's pricing pages — E3's list price took effect July 1, 2026. Litigation-hold and auto-expanding-archiving licensing rules (Plan 2, or Plan 1 + Archiving add-on; 1.5 TB ceiling) per Microsoft Learn's Exchange Online limits and litigation-hold documentation. List prices are annual-commitment; monthly terms cost more.
Editorial note: two gotchas to avoid. First, removing the add-on disables the archive — so don't let a tidy-up pass at true-up remove licenses from mailboxes that have holds or archives attached. Second, the add-on expands archive storage, not the primary mailbox — if the primary mailbox itself is the problem, that's a different license conversation.
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