SMTP enhanced status code 5.3.4

What the registry says

The basic codes it travels with

• 552 Requested mail action aborted: exceeded storage allocation
• 554 Transaction failed (Or, in the case of a connection-opening response, "No SMTP service here")

In practice

Size limits vary by server: Gmail names its message, attachment and header limits in the reply text, and other servers set their own caps. Attachments grow by about a third when base64-encoded, so a file under the limit on disk can exceed it in the message. A message that fails with 5.3.4 will fail every time, so shrink it or send a link.

What the sender should do

Remove large attachments and share them as links, or compress them, then resend.

How providers use X.3.4

Quoted from each provider’s own error reference.

• Gmail 552 5.3.4

  Your message exceeded Google's message size limits. To view our message size guidelines, go to Send attachments with your Gmail message.

Common questions

What does 5.3.4 mean?

X.3.4 means the message is bigger than the receiving system's per-message size limit. It is permanent for that message, and the same message will fail every time.

What should I do about 5.3.4?

Remove large attachments and share them as links, or compress them, then resend.

Would an email verifier have caught 5.3.4?

No. This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.

Full guides for this code

• 552 5.3.4 — message too big