Recoverable Items: 14 days, 30 GB and the day the mailbox can no longer delete

Every Exchange Online mailbox has a folder that never shows up in Outlook and that is the one saving you the day somebody empties Deleted Items with something in it. It is called Recoverable Items and it has two limits almost nobody has ever looked at: it keeps things for 14 days by default and it holds 30 GB. Put the mailbox on hold and the ceiling rises to 100 GB — in exchange for the folder never draining again: from then on, things only go in. And on the day it hits that ceiling — this is Microsoft's own documentation talking, not us — the user cannot delete, versions of what they edit stop being kept and audit entries stop being written. The control you put in place to preserve everything breaks in exactly the place where it was supposed to hold.

What follows is how you measure that in a real tenant, with two commands, and what to do with the answer. There is no trick and no hidden setting: it is all published and has been there for years. It is simply one of those things nobody looks at until it has already failed, and by then the symptom reaching the service desk is not "a system folder filled up" but "I cannot delete this email", which sounds like nothing at all.

Where the things you delete actually go

There are three verbs and it pays not to mix them up. Delete means sending something to the Deleted Items folder, the ordinary bin. Soft delete is what happens when the user empties that bin or hits Shift+Delete: the item leaves the view and lands in Recoverable Items. Hard delete is when the item is marked to be purged from the database. Only the second step is what people mean by "I deleted it for good", and it is precisely the one that can still be undone.

Recoverable Items lives in the mailbox's non-IPM subtree, the part no mail client ever shows. Inside there are more folders than most people know about: Deletions (the only one the user sees, through "Recover deleted items"), Versions (prior copies of modified messages, only when a hold is in place), Purges (hard-deleted items, when there is a hold or single item recovery), DiscoveryHolds, SubstrateHolds (Teams messages), Audits and the calendar log. And it has its own quota: when an item moves here, its size is deducted from the mailbox quota and added to this folder's.

The two clocks: 14 days and 30 GB

The first one is time. An Exchange Online mailbox keeps permanently deleted items for 14 days by default, and you can raise that to a maximum of 30. There is no 60, no 90, no "set it to whatever you like": thirty and that is it. You change it per mailbox or in one go:

Set-Mailbox -Identity "[email protected]" -RetainDeletedItemsFor 30

Get-Mailbox -ResultSize unlimited -Filter "RecipientTypeDetails -eq 'UserMailbox'" |
    Set-Mailbox -RetainDeletedItemsFor 30

And here comes the first detail that bites, because it sits in a footnote of the documentation itself: "these commands only apply to existing mailboxes and will not affect new mailboxes that you create in the future". So you raise it to 30 days today, tick the box, and the salesperson who joins in October starts on 14 without anyone noticing. To make the value the house default you have to touch the mailbox plan with Set-MailboxPlan, not the mailbox. It is exactly the kind of setting you configure once, document, and never look at again until somebody compares two mailboxes and the numbers do not match.

The second clock is size. The Recoverable Items quota in Exchange Online is 20 GB warning and 30 GB hard limit. As long as the mailbox is not on hold, the system looks after itself: the Managed Folder Assistant purges whatever has aged out, and if the warning quota is reached before the retention period expires, it starts purging first in, first out. Put differently: with no hold in place, the folder self-cleans and you will never see the ceiling. With one nice exception — calendar items, which are purged after 120 days rather than 14.

And a caveat that the page itself carries, which changes who the first clock is for: "if you place a mailbox on litigation hold, the retention limit is ignored". Raising it to 30 days is the cheap win for the rest of the estate, but it does nothing for the mailboxes this article is about. On those, the clock that rules is the other one: the gigabytes.

The two commands that tell you your headroom

The first one measures the folder. The RecoverableItems scope returns the folder plus its Deletions, DiscoveryHolds, Purges and Versions subfolders, which is exactly the breakdown you want in order to know what is filling the bucket:

Get-EXOMailboxFolderStatistics -Identity "[email protected]" -FolderScope RecoverableItems |
    Format-Table Name, FolderAndSubfolderSize, ItemsInFolderAndSubfolders -AutoSize

Get-Mailbox -Identity "[email protected]" | Format-List `
    RetainDeletedItemsFor, SingleItemRecoveryEnabled, LitigationHoldEnabled, InPlaceHolds, ArchiveStatus

The second tells you which regime that mailbox is under, which is what decides everything else: how many days it keeps, whether there is a litigation hold, whether Purview retention is applied and — this matters a great deal, as you will see — whether the archive is enabled. Microsoft recommends Get-EXOMailboxFolderStatistics over the classic Get-MailboxFolderStatistics when working against Exchange Online; the classic one still works and takes the same scopes.

A hold raises the ceiling and closes the drain

The moment you put a mailbox on Litigation Hold, In-Place Hold or under a Microsoft 365 retention policy, two things happen at once. The good one: the quota is automatically raised from 20/30 GB to 90 GB warning and 100 GB limit (and to 95/105 if the archive is also enabled). The bad one: putting a mailbox on hold stops the Managed Folder Assistant, which no longer purges automatically from DiscoveryHolds, Deletions and Purges. Copy-on-write page protection also kicks in, saving a prior copy of every item the user modifies.

Add it up: more goes in (now including a version of every message that gets touched) and nothing comes out. A folder that only grows, with a hard limit, is a countdown. And this is what the documentation says happens when it runs out, word for word:

• Mailbox users cannot delete items.
• The Managed Folder Assistant cannot delete items based on retention tags.
• Copy-on-write page protection cannot maintain versions of items edited by the user.
• If mailbox audit logging is enabled, no audit log entries are saved in Audits.

Read them again with the question of why you put the hold there in the first place. You put it there to preserve what gets deleted, to preserve prior versions of what gets edited, and to be able to prove afterwards who did what. The last three bullets on that list are precisely those three things ceasing to work. And there is no warning: nobody gets an email, no alert fires in the admin centre. The only thing that happens in the real world is that Outlook will not let somebody delete a message, and that person is going to report it as an Outlook problem.

The drain exists. Almost nobody has connected it.

The Default MRM Policy that is automatically applied to new Exchange Online mailboxes ships with a tag called "Recoverable Items 14 days move to archive". It does what it says: after 14 days it moves whatever is in the primary mailbox's Recoverable Items to the Recoverable Items folder of the archive. That is the drain. And it comes as standard. With one caveat: whatever sits in Deletions is governed first by your RetainDeletedItemsFor, and only then starts that journey. The sentence almost nobody has read is this one: "for this to happen, the user's archive mailbox must be enabled. If the archive mailbox isn't enabled, no action is taken".

That is the knot. The draining mechanism ships configured and does absolutely nothing while the archive is left disabled. With the archive enabled and auto-expanding archiving turned on, the primary mailbox folder goes to 110 GB and the archive plus Recoverable Items together reach up to 1.5 TB. And if you want the drain to run at the same pace as your deleted item retention period, Microsoft's own guide recommends creating a custom tag and matching the two:

New-RetentionPolicyTag -Name "Recoverable Items 30 days for mailboxes on hold" `
    -Type RecoverableItems -AgeLimitForRetention 30 -RetentionAction MoveToArchive

Start-ManagedFolderAssistant "[email protected]"

The second command exists because the assistant can take up to 7 days to process mailboxes with the new settings, and seven days waiting to see whether something works is a long time. And one honest warning before you press the button: enabling the archive also means the default policy starts moving mail older than two years into it. Things will disappear from the user's primary mailbox — they will still be there, in another folder — and if you have not told them beforehand, that is tomorrow's ticket. We covered it in more detail in what happens when you archive by policy.

The folder that does not come back, not even under litigation hold

This is the hardest fact in the whole article to swallow, and the one fewest people know. If a user hits Shift+Delete on a folder they created themselves, or deletes a folder sitting inside Deleted Items, that folder is hard deleted and cannot be recovered even if the mailbox is on litigation hold or In-Place Hold. Its contents do drop into Deletions and can be recovered for 14 days. It does not apply to the default folders — Inbox, Sent Items, Drafts, Deleted Items, Junk Email, Archive, Outbox — which are not going anywhere.

Translated into what happens to an actual person: the hold preserves items, not structure. A project manager with a folder per client who deletes the parent folder does get all their mail back — as one flat pile. With years of mail inside it, that is not a recovery, it is a penance. And no legal hold, however expensive, gives you the folder tree back. Only a copy taken outside does that.

When this is not your problem

If your tenant has no holds in place, no litigation holds and no Purview policies applied to mailboxes, this article is a curiosity and nothing more. The mechanism self-cleans, the quota never gets near the ceiling and you will never see the problem. Raise the retention period to 30 days — it is free, it takes a minute and it is the one thing here that helps everybody — and get on with your day.

And if your only worry is "somebody deleted an email this morning", those fourteen or thirty days are plenty and you do not need to buy anything from anyone. We say it plainly because it is true, even though it does not help us sell. This starts to matter in a different way when there are holds in place, when there are mailboxes with eight years of history inside them, when someone turned on auditing so they could answer an awkward question two years from now, or when what got deleted was not an email but an entire folder.

Six checks for this morning

• List the mailboxes on hold (LitigationHoldEnabled or a non-empty InPlaceHolds) and measure their Recoverable Items folder. They are the only ones that can hit the ceiling.
• Of those, check which have the archive enabled. The ones that do not are the ones with the drain shut.
• Write down today's size for each one, with the date. Without a second measurement you have no slope, and without a slope you have no deadline.
• Raise RetainDeletedItemsFor to 30 on existing mailboxes and on the mailbox plan, or the next new hire will be born with 14 days again.
• If you are going to enable archives, tell the users the day before what they are about to see. It costs one email and saves you an afternoon.
• Ask yourself what you recover if a folder with years of mail inside it disappears tomorrow. If the answer is "the emails, without the folders", you already know what is missing.

What a copy taken outside buys you

None of this is a defect in Exchange Online: it is a safety net that does what it says on the tin and has it published. It is just that its three properties are rarely stated one after the other. It runs out: 30 GB, or 100 GB with a hold. It switches off when it fills, and the three things it stops doing are the three you put it there for. And it lives in the same place as the original, inside the same tenant, subject to the same policies and the same administrative mistakes — which is what we wrote about in why a copy that never leaves Microsoft is not a copy and in why retention is not a backup.

Our Backup 365 service exists because of those three sentences, not because of a catalogue: a copy that leaves the tenant and has its own retention schedule. And with it comes the question to put to any backup tool, ours included, before you sign for it: does it give me the mailbox back with its folder tree, or a heap of loose messages? That is the test that separates a copy from a filing cabinet. And the boring work above — going through which mailboxes are on hold, which have an archive, what period is set on the plan — is part of how we run a Microsoft 365 tenant, with the support desk that picks up the "I cannot delete an email" ticket knowing what sits behind it.

Sources (verified one by one): Recoverable Items subfolders, the 14-day default retention period, calendar items purged after 120 days, FIFO purge on reaching the warning quota, the 20/30 GB and 90/100 GB quotas, the rise to 95/105 GB with an archive, the behaviour on reaching the quota (the four bullets quoted), the Managed Folder Assistant stopping under a hold, copy-on-write and the hard deletion of user-created folders — Microsoft Learn, "Recoverable Items folder in Exchange Online"; the 30-day maximum, the Set-Mailbox -RetainDeletedItemsFor commands and the note that they do not affect new mailboxes — Microsoft Learn, deleted item retention; the "Recoverable Items 14 days move to archive" tag in the Default MRM Policy, the requirement that the archive be enabled, the 110 GB and 1.5 TB with auto-expanding archiving, New-RetentionPolicyTag and the assistant's 7 days — Microsoft Learn, Recoverable Items quota for mailboxes on hold (that page still carries a scope notice for 21Vianet-operated organisations following the retirement of classic eDiscovery; the Default MRM Policy tag and its 14 days are separately confirmed in Default Retention Policy in Exchange Online); the RecoverableItems scope and the recommendation to use Get-EXOMailboxFolderStatistics — cmdlet reference. All consulted on 29 August 2026. The monthly-slope arithmetic is ours and comes from two measurements of your own, not from any published statistic. The commands are the ones in the official documentation: try them against a mailbox that does not matter first.