SMTP 552: requested mail action aborted, exceeded storage allocation
A storage or size limit stopped the message: the recipient's mailbox is full, or the message is larger than the receiver accepts.
552 5.3.4 Your message exceeded Google's message size limits.
Start of Gmail's text for an oversized message, as listed in Google's SMTP errors reference.
What 552 means
RFC 5321 defines 552 as "Requested mail action aborted: exceeded storage allocation". It is a permanent reply, but the enhanced code tells you which limit you hit.
- 5.2.2 Mailbox full. The recipient is over their quota. RFC 3463 says this code should be used as a persistent transient failure, because the recipient can delete messages to make room.
- 5.2.3 Message length exceeds administrative limit. A per-mailbox size limit lower than the server's general limit.
- 5.3.4 Message too big for system. The message is larger than the server's per-message limit. Gmail returns 552 5.3.4 for messages, attachments or headers over its limits.
One historical quirk: RFC 821 used 552 for "too many recipients". RFC 5321 corrects this to 452 and asks clients to treat a 552 for too many recipients as temporary. And RFC 5321's size-limit section gives "552 Too much mail data." as an example reply for a message that is too large.
Likely causes
- The recipient's mailbox is full.
- The message, with attachments, is larger than the receiver accepts.
- Headers are larger than the receiver accepts.
- An older server reporting too many recipients with 552.
How to fix it
If you sent the message
- For a size error, send large files as a download link instead of an attachment.
- Remember that attachments grow by about a third when encoded for email.
- For a full mailbox, contact the recipient another way and resend once they have cleared space.
If you're the recipient or their admin
- Delete or archive old mail, or ask your admin for a larger quota.
- If partners need to send large files, agree on a file-sharing method.
Frequently asked questions
How do I know if 552 means mailbox full or message too big?
Read the enhanced code. 5.2.2 means the recipient's mailbox is full; 5.3.4 means your message is larger than the receiving system allows; 5.2.3 means a per-mailbox size limit.
Why does my 20 MB attachment fail when the limit is 25 MB?
Email usually encodes attachments with Base64 (RFC 2045), which turns every 3 bytes into 4 characters, so files grow by about a third. A file close to the limit can end up over it once encoded.
Sources
- RFC 5321: Simple Mail Transfer Protocol (reply codes, section 4.2)
- RFC 3463: Enhanced Mail System Status Codes
- Gmail SMTP errors and codes (Google Workspace Admin Help)
- RFC 2045: MIME part one, section 6.8 (Base64 encoding)
Provider messages are quoted as the provider publishes them. Servers can change their wording, so the bounce you received may differ slightly.
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