SMTP 552
A permanent-form reply meaning the message exceeded the recipient's storage allocation. In practice this is usually a full mailbox rather than a dead one.
In plain terms
The mailbox is full — the address itself is probably fine.
Why it matters for deliverability
552 is the code most often mis-classified. Its 5xx form implies permanence, but RFC 5321 pairs it with the transient 452 for the same size and quota conditions and tells clients to expect either. Treating every 552 as a hard bounce quietly deletes real subscribers who simply need to empty their inbox.
What to do about it
- Do not suppress on a single 552.
- Retry only when the cause is recipient storage. If the rejection is about message size, resending the same message unchanged will fail again — reduce the size instead.
- Suppress only after a storage condition persists across several sends over weeks.
- Track 552 separately from 550 in reporting — collapsing them hides a real difference.
Source
RFC 5321 — Simple Mail Transfer Protocol
“552 Requested mail action aborted: exceeded storage allocation”
Checked 2026-08-29
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