Outlook 0x8004060C: The Mailbox or Outlook Data File Has Hit Its Size Limit

Fix it now

Something the mailbox writes into is full and there are three candidates: the server mailbox quota, the Outlook data file’s own maximum, or the disk beneath it. Establish which before you delete anything, because the fix for each is different.

1. For a Microsoft 365 or Exchange account, read the mailbox usage indicator under File, Info. For a local data file, read the file size on disk instead.
2. Empty Deleted Items, then clear what sits behind it: on the Folder tab choose Recover Deleted Items, select everything and purge.
3. Find the large items. Switch a folder to the Size arrangement, or use the mailbox cleanup tool under File, Tools.
4. Move old mail into the online archive if the licence provides one, or into a second Outlook data file if it does not.
5. For a local data file, compact it after deleting. Deleting alone marks space reusable inside the file; it does not shrink the file on disk.
6. If the mailbox is genuinely at the size its plan allows, stop housekeeping and read the licensing section below.

The default maximum for a Unicode Outlook data file on Outlook 2016 and later is 51,200 MB, with a warning at 48,640 MB. A file at either number is at a configured ceiling, not damaged.

If mail sends and arrives again, you are done. The next section separates the three ceilings, which is where most of the wasted effort on this error goes.

Why it happens

Three separate limits produce an identical write failure inside Outlook. A server mailbox has a quota set by the plan and by your administrator, with warning, prohibit-send and prohibit-send-and-receive thresholds stacked beneath it. A local Outlook data file has a maximum enforced by Outlook rather than by the file system. And the disk under the data file can simply run out of room, which is what 0x8004010D reports: not enough disk space was available to complete the operation.

The quota states explain the sequence users describe. Below the warning level everything is normal. Above it, warnings arrive. Above prohibit-send you can still receive but not send, which is the stage where most people notice. Above prohibit-send-and-receive, inbound mail stops. Recoverable Items has its own separate quota, and on a mailbox under a hold that area can fill while the visible folders look modest.

The data file ceiling is a documented, adjustable number rather than a mystery. On Outlook 2016 and later a Unicode file defaults to a maximum of 51,200 MB with a warning at 48,640 MB, both set in megabytes. The much older ANSI format has separate values expressed in bytes and a hard two-gigabyte wall that Outlook enforces regardless of what the registry says, to prevent corruption.

One warning about bounce codes. Microsoft’s Exchange Online reference publishes 5.2.2 as Submission quota exceeded – the sender exceeded the recipient rate limit or the message rate limit – not as a full recipient mailbox. If a sender shows you a 5.2.2 bounce, read it as a rate limit on the sending side until you have separate evidence of the recipient’s quota.

Full reference

Which ceiling you have hit

The data file size values, as published

The policy location is HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook\PST for Outlook 2016; earlier versions use their own version number in the same position. A user-preference location exists at the equivalent path without Policies. If MaxFileSize is ever set above the ANSI two-gigabyte limit the value is ignored and the size is held at 2 GB, which is deliberate, to prevent corruption.

Mailbox and archive capacity by plan

Auto-expanding archiving starts each user at 100 GB of archive storage and adds more automatically as that fills, up to 1.5 TB including the Recoverable Items area. On a mailbox on hold, the Recoverable Items quota in the primary mailbox is 100 GB. Those two numbers together are why a mailbox on hold behaves so differently from one that is not.

Reading a bounce correctly

Exchange Online’s non-delivery report reference is the place to check a code rather than a search engine. 5.2.2 there is Submission quota exceeded, pointing at the sender’s rate limits. 5.2.3 does not appear in that table at all. If the sender’s bounce carries a code you cannot find in Microsoft’s list, ask them for the full report headers rather than guessing at what the number means.

Stopping it coming back

• Put a retention or archive policy in place so old mail moves out on its own rather than accumulating until someone notices.
• Set the offline cache slider to something sensible so the local file does not grow without limit on a large mailbox.
• Watch usage rather than waiting for bounces; the warning threshold exists so that somebody acts before the prohibit thresholds bite.
• Split very large personal data files rather than raising their ceiling, because everything about a large file gets slower and repair gets slower fastest.

Every code this article covers

Confirm the fix worked

1. A test message leaves the affected mailbox.
2. Someone outside the organisation can reply and it arrives without a bounce.
3. File, Info shows usage below the warning threshold.
4. For a local data file, the file size on disk has actually fallen after compacting.
5. Nothing has reappeared a week later, which is the test of whether the archive policy is doing its job.

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