Bounce Codes
552 5.2.2 Permanent Failure Mailbox full (permanent quota failure)
Distinct from the temporary 452 code — some mail servers escalate a persistently over-quota mailbox to a permanent failure after repeated attempts, effectively treating "always full" as "doesn't exist" for delivery purposes.
Common causes
- Long-abandoned mailbox that's been over quota for an extended period.
- Receiving server configured to permanently reject rather than queue for chronically full mailboxes.
What to do
Treat as a hard bounce and suppress. An address returning a permanent (5xx) full-mailbox code rather than a temporary (4xx) one has typically already been unreachable for a sustained period.
FAQ
Why would a mailbox being full be a permanent failure instead of temporary?
Server configuration choice — some mail systems decide that after enough failed delivery attempts, continuing to queue and retry isn't worthwhile, and convert the response to permanent to stop further retry attempts from senders.
Catch These Before You Send
100 free credits — work email application after signup, no card required.
Sign up