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RFC 3463 / ENHANCED MAIL STATUS

Locate the cause with the subject and detail together

03

A repeated detail number can mean different things under different subjects. Compare an address error, a mailbox condition and a system-wide storage condition.

DIAGRAMRead RFC section 3 ↗
RFC 3463 · § 3EXAMPLE
3 / 3
Locate the cause with the subject and detail togetherThree cause comparisons.5.1.1uses addressing subject1and detail1for a nonexistent destination mailbox.4.2.2uses mailbox subject2and detail2for a per-mailbox quota or capacity problem.4.3.1uses mail system subject3and detail1for shared system storage exceeded, where the recipient may not be able to free space. Detail1does not have a global meaning independent of subject. Only selected cases are illustrated; no complete diagnosis or registry validator is supplied.The subject changes the meaning of detail4.3.1Subject 3: Mail systemShared storageFULLIndividual deletion may not make roomDetail 1: mail system full
03
System subject: shared storage is exhausted.

4.3.1 selects Mail System Status plus Mail system full. Detail1 now describes system storage, not an address. The receiver’s shared storage is the boundary.

Source for this drawing: RFC 3463 · Read RFC section 3 ↗

Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references
New to this? Start hereA quick picture + helpful background

The envelope and the letter do different jobs.

Mail transport moves a message between servers. The message format describes its contents. Authentication adds checks; it does not make every message safe.

Helpful first, if these ideas are unfamiliar

RFC 5321 SMTP RFC 2033 LMTP local delivery RFC 5322 Email message format

These pictures are analogies to help you learn. The linked RFC explains the actual rules.

Related RFCs and changes

“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.

KEY POINT

A mailbox limit and a system-wide limit belong to different subjects.

  • The original subject families are 0 other/undefined, 1 addressing, 2 mailbox, 3 mail system, 4 network/routing, 5 delivery protocol, 6 content/media and 7 security/policy.
  • 5.1.1 identifies a bad destination mailbox address: for an Internet address, the part to the left of @ is invalid. It is not a full mailbox.
  • 4.2.2 denotes mailbox quota/capacity; 4.3.1 denotes system storage exceeded. With a system-wide shortage the individual recipient may be unable to free enough storage. These are selected RFC examples, not a complete fault-diagnosis procedure.
DETAILS

Other distinctions include permanent per-mailbox size limit X.2.3 versus system-wide message-size limit X.3.4. The X is a class placeholder and does not mean every class is appropriate for every detail. The name of a probable cause is not evidence that a status producer diagnosed it correctly.

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