Documentation
Mailbox full: 5.2.2 and 4.2.2.
The address is real, but the mailbox has no room for the message.
What it means
The receiving server accepted the address and then refused the message because the mailbox is over its quota. The status code tells you how it will be treated: 4.2.2 is temporary, and 5.2.2 is permanent. Mailtruss reads the code and classifies the bounce the same way.
Typical codes and wording
552 5.2.2 (permanent), 452 4.2.2 (temporary)
Common causes
- A personal mailbox that is genuinely full and has not been cleared.
- An abandoned mailbox that nobody reads.
- A shared or role mailbox (such as info@) that collects more than it can store.
What to do
- If the bounce was temporary (4.2.2), you can send again later. The delivery network already retried for a while before reporting it, and it does not retry again by itself.
- If it was permanent (5.2.2), reach the person another way, or remove the address.
- If the same address keeps reporting a full mailbox over weeks, treat it as abandoned and stop sending to it.
What Mailtruss shows
Titled "Recipient mailbox is full". A temporary one is marked safe to retry; a permanent one is not, and the address is added to your suppression list.
Is it safe to retry?
Later, if it was temporary. Not if it was permanent.