552 5.2.2 Mailbox Full: What the Sender and Recipient Do

Your message came back with a code reading 552 5.2.2 mailbox full — sometimes phrased as "recipient mailbox is over quota" or "user over quota." This page explains what that code means, what the sending server has already done with your message, and what the sender and recipient can each do to resolve it. It also covers how 552 5.2.2 differs from the similar-looking 452 4.2.2 code, which behaves differently and requires a different response.

What This Error Literally Means#

The 552 and 5.2.2 in this bounce are two separate codes describing the same rejection from different angles.

552 is the SMTP reply code. Any code in the 500 range signals a permanent failure: the receiving server has rejected the message definitively, the sending server removes it from the outbound queue, and no automatic retry will happen. Compare this to 452, which is in the 400 range and signals a temporary condition — the sending server queues the message and keeps retrying, typically for several days.

5.2.2 is the enhanced status code defined in RFC 3463. The three-part structure is class.subject.detail. Class 5 means permanent failure. Subject 2 covers Mailbox Status. Detail 2 means the recipient's mailbox has exceeded its per-mailbox administrative quota or physical capacity. RFC 3463 notes that X.2.2 should ideally be issued as a transient failure (4xx), meaning 452 4.2.2 is the technically preferred code for a retryable full-mailbox condition. In practice, many servers issue 552 5.2.2 instead, and when they do, the sending server treats it as permanent.

The practical implication is that when you receive a bounce notification with 552 5.2.2, the sending server has already made its final decision. The message will not deliver automatically. You must send it again manually, and only after the recipient has cleared enough storage to accept it.

What Causes a 552 5.2.2 Bounce#

Four situations commonly produce this bounce. The table below maps each cause to how you confirm it and what both parties can do.

Fix 1: What the Sender Can Do#

The sender's options are limited by design. A 5xx SMTP rejection means the receiving server will not accept the message until the mailbox has space, and the sending server will not try again automatically. The steps below work around that constraint.

1. 1

   Stop resending immediately

   Every attempt hits the same full mailbox and produces the same 552 bounce. Repeated sends do not help and may trigger rate-limit warnings on the receiving server.

2. 2

   Contact the recipient through another channel

   Phone, Slack, Teams, or SMS. Let them know their inbox is full. The bounce notification goes to the sender, not the recipient, so most recipients are unaware until someone tells them directly.

3. 3

   Wait for confirmation before retrying

   Once the recipient confirms they have cleared space, send the message again manually. The sending server will never retry on its own after a 552 response — you have to initiate the send.

4. 4

   Strip the attachment and share via a cloud link

   If the original message included a large attachment, share the file through Google Drive, OneDrive, or Dropbox and send only the link in the email body. This removes the storage burden from the recipient's mailbox entirely.

5. 5

   Verify the problem is not on your end

   Send a short test message to a different recipient. If that delivers, the issue is specific to this recipient's mailbox and not your sending domain or server configuration.

Fix 2: What the Recipient Can Do in Gmail#

Google accounts share one storage pool across Gmail, Drive, and Photos. When that pool fills, Gmail rejects incoming mail with a 552 5.2.2 response before the message is accepted. The steps below free up space so new mail can arrive.

1. 1

   Check actual storage usage by service

   Go to storage.google.com. The breakdown shows exactly which service is consuming the most space. Many accounts find Drive or Photos is the main culprit, not Gmail itself.

2. 2

   Delete large messages in Gmail

   In the Gmail search bar, type: has:attachment larger:5M — then sort by size and delete the largest items first. Repeating the search with larger:10M targets the biggest messages quickly.

3. 3

   Empty Spam and Trash completely

   Gmail counts messages in Spam and Trash toward your quota until they are permanently deleted. Open each folder and select Empty Spam Now and Empty Trash Now to remove them.

4. 4

   Clear large files in Drive and Photos

   Use the Storage management page at drive.google.com/settings/storage to identify large files. Videos and high-resolution photo libraries are usually the biggest items and the fastest wins.

5. 5

   Upgrade storage if routine management is not enough

   If you regularly receive high volumes of mail with attachments, upgrading Google One adds storage across all Google services. The 100 GB tier is typically the first paid option available.

Fix 3: What the Recipient Can Do in Outlook and IMAP Mailboxes#

Outlook and Exchange mailboxes have a quota set by the account plan or the IT admin, separate from any cloud file storage. IMAP mailboxes at hosting providers — cPanel, Fastmail, Proton, and similar — have their own per-account limits set by the host.

1. 1

   Check your mailbox size in Outlook

   In Outlook for Windows, go to File, then Info, and look for Mailbox Cleanup. It shows current mailbox size and lets you find large items sorted by size. In Outlook on the web, go to Settings and search for Storage.

2. 2

   Archive old mail to free space

   In Outlook for Windows, use File, then Cleanup Tools, then Archive to move older messages to a local PST file. If your Microsoft 365 plan includes an Online Archive, enabling it through the Exchange Admin Center adds significant extra capacity.

3. 3

   Empty Deleted Items and Junk Email

   Right-click each folder and select Empty Folder. Outlook counts both folders against your quota until messages are permanently removed — they do not free space until emptied.

4. 4

   Ask your IT admin to raise your quota

   On a corporate Exchange or Microsoft 365 plan, the mailbox size limit is an admin-controlled setting. If archiving alone does not solve the problem, a quota increase is the most direct and permanent fix.

5. 5

   For IMAP and hosted mailboxes, log into webmail

   cPanel, Fastmail, and Proton Mail all provide a webmail interface that shows storage usage. Delete the largest messages, empty Trash, and contact your host's support team if you need the account quota raised.

How to Tell Which Cause You Have#

The bounce notification your email client shows contains enough detail to identify the cause. Look at three things.

First, read the SMTP response text in the bounce. Providers include plain-language detail alongside the numeric codes. Gmail typically writes something like: The email account that you tried to reach is over quota. Exchange writes: Mailbox size limit exceeded. Hosting providers vary, but most include the words quota or limit.

Second, look at the recipient's email domain. A @gmail.com or @googlemail.com address means Google's shared storage pool is the cause. A corporate domain points to Exchange or Microsoft 365. Addresses at Fastmail, Proton, iCloud, or Yahoo use each provider's own per-account quota.

Third, consider whether the message carried a large attachment. If the file was over 10 MB and the bounce happened on only this one email to this one recipient, a nearly-full mailbox tipped over the edge is the most likely explanation. Test by sending a short message without any attachment to the same recipient — if that still bounces with 552, the entire mailbox is full. If the short message delivers, the attachment was the tipping point.

Preventing 552 5.2.2 Bounces#

Most 552 5.2.2 rejections are avoidable. Storage fills gradually over months, then hits the limit at the worst possible moment.

Monitor your quota before it fills. Gmail, Outlook, and most hosted providers display a storage bar in account settings. Check it quarterly and act before reaching 90 percent — clearing space under time pressure is harder than doing it as routine maintenance.

Send files as links rather than attachments wherever possible. A 20 MB video attached to an email permanently occupies 20 MB of the recipient's mailbox quota. The same file shared via a Drive or OneDrive link occupies zero mailbox quota on the recipient's end.

Set up archiving rules. Outlook's AutoArchive moves mail older than a set threshold to a local file automatically. Gmail's Storage management tool flags large, old messages. Both reduce the accumulation rate before it becomes a problem.

IT admins: configure quota warnings at 80 percent so users get advance notice rather than discovering the limit when a sender complains. Most Exchange and hosted providers support configurable warning thresholds.

We build AI Emaily, an AI-native email client whose autonomous triage applies filing and archiving rules continuously: newsletters and bulk mail are categorised out of the primary inbox on arrival, which slows the storage accumulation rate, and the audit log surfaces bounce events — including 552 rejections — as labelled items rather than silently lost messages. None of that replaces clearing actual storage quota, but it substantially slows the refill rate between manual cleanups.