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RFC 8058 / ONE-CLICK EMAIL UNSUBSCRIBE

Encode the fixed POST body without changing the target

04

The same key/value pair can be sent as an allowed URL-encoded form or as recommended multipart form data. Body encoding does not change the HTTPS URI.

DIAGRAMRead RFC section 3.2 ↗
RFC 8058 · § 3.2EXAMPLE
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Encode the fixed POST body without changing the targetSchematic HTTP request anatomy for two permitted encodings. URL-encoded public example uses unchanged unsubscribe opaquepart target and the exact26 ASCII octet body. Corrected multipart example uses unsubscribe.html slash opaque123456789 with no added equals sign and boundary parameter -FormBoundaryjWmhtjORrn. The next state expands the124 octet body: two-hyphen prefix plus boundary, Content-Disposition name List-Unsubscribe, empty line, One-Click, closing delimiter. CRLF separates lines; no final CRLF is included in this chosen RFC example. Verified errata5117,8927,5559 applied; rejected5558 not adopted.One fixed action, two permitted encodingsMultipart body; CRLF between lines---FormBoundaryjWmhtjORrnContent-Disposition: form-data;name="List-Unsubscribe"[one empty line]One-Click---FormBoundaryjWmhtjORrn--124 ASCII octets in this exampleNo CRLF after the closing delimiter
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Construct the corresponding multipart part.

Delimiter lines add two hyphens to the parameter value. The part name and One-Click value encode exactly the same action; the closing delimiter adds two terminal hyphens.

Source for this drawing: RFC 8058 · Read RFC section 3.2 ↗

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KEY POINT

Encode one fixed form field and keep the advertised target intact.

  • The receiver performs an HTTPS POST to the HTTPS URI in List-Unsubscribe, with the List-Unsubscribe-Post key/value pair as its body.
  • The content SHOULD use multipart/form-data; application/x-www-form-urlencoded MAY be used. The single field is List-Unsubscribe with value One-Click, not arbitrary extra form arguments.
  • Verified errata5117/8927 correct the multipart boundary parameter to -FormBoundaryjWmhtjORrn. Verified erratum5559 removes the stray equals sign in the multipart request target. A delimiter is two hyphens plus the boundary value.
DETAILS

Public examples adapted from§8.1/§8.3 with verified errata. Header anatomy is schematic, not a full HTTP transcript. The URL-encoded body is26 ASCII octets. The illustrated multipart body uses CRLF between its lines and no trailing CRLF after the closing delimiter, yielding124 octets as in the RFC; rejected erratum5558 is not an adopted correction. This is not a full multipart tutorial.

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