452 4.2.2 (and the older 552 5.2.2) means the recipient's mailbox is full. Their storage is used up, so the server cannot accept new messages for now. The address is real; there is just no room.

It is one of the few bounces that is not your fault and not permanent, but it can still tell you something useful about the address. For every other code, see our guide to SMTP bounce codes.

What the error looks like

Provider Typical message
Gmail and Google Workspace 452 4.2.2 The email account that you tried to reach is over quota.
Other servers 552 5.2.2 Mailbox full or Quota exceeded

Gmail storage is shared between Gmail, Google Drive and Google Photos, so a mailbox can fill up because of photos or files, not only email.

What it means

  • 452: a temporary failure ("insufficient system storage").
  • 4.2.2: "mailbox full". The .2 in the middle means the problem is the mailbox, not the address.

You may also see 552 5.2.2, with a 5. Even then, the standards treat a full mailbox as a condition that can clear, so most senders handle it as a soft bounce.

What to do

  1. Nothing, at first. Your sending server retries soft bounces on its own for a while. If the person frees up space, the message gets through.
  2. Do not resend manually, or the person may get the same message twice later.
  3. Watch for repeats. If the same address is full across several campaigns over weeks, the inbox is very likely abandoned: someone stopped using it and let it fill up. Many senders suppress an address after three to five consecutive soft bounces. Treat a mailbox that has been full for months like a hard bounce.
  4. If the message matters, reach the person another way and let them know their mailbox is full.

Why a full mailbox is a warning sign

Active users notice when their mailbox is full; it blocks their own mail. A mailbox that stays full is usually one nobody reads anymore. Sending to it brings no opens, and abandoned addresses are sometimes turned into spam traps later. See spam traps.

How email verification handles it

When MailQuell checks an address and the server answers "mailbox full", the address is reported as inbox full instead of safe or invalid: the mailbox exists, but your message would not arrive today. Those addresses are worth leaving out of an important send, or checking again later.

Frequently asked questions

Is 452 4.2.2 a hard or a soft bounce?

Soft. The address exists, and the problem can clear on its own.

Why do I get 552 5.2.2 with a 5 if it is temporary?

Some servers report it as permanent for that delivery attempt. The underlying condition (no space) is still one that can change, so retry later rather than deleting the address straight away.

How long should I keep retrying?

Your sending server handles retries for the current message (usually up to a few days). Across campaigns, suppress the address after it stays full on several consecutive sends.

Sources