RFC 9051, "Internet Message Access Protocol (IMAP) - Version 4rev2", August 2021

Errata ID: 7246
Status: Reported
Type: Technical
Publication Format(s) : TEXT
Reported By: Mechiel Lukkien
Date Reported: 2022-11-12

Section 7.5.2. says:

   BINARY[<section-binary>]<<number>>
      An <nstring> or <literal8> expressing the content of the specified
      section after removing any encoding specified in the corresponding
      Content-Transfer-Encoding header field.  If <number> is present,
      it refers to the offset within the DECODED section data.

It should say:

   BINARY[<section-binary>]
      An <nstring> or <literal8> expressing the content of the specified
      section after removing any encoding specified in the corresponding
      Content-Transfer-Encoding header field.

Notes:

While a FETCH _request_ can be "partial" with <...> for both BODY[] and BINARY[], only a FETCH _response_ for BODY[] can have an optional offset. A FETCH _response_ for BINARY[] cannot have an optional offset. At least according to the ABNF, which I believe is leading.
See lines 6756 and 6757: msg-att-static = "BODY" section ["<" number ">"] SP nstring / "BINARY" section-binary SP (nstring / literal8)
And line 6987: section-binary = "[" [section-part] "]"

RFC 3516, IMAP4 Binary Content Extension, from which the original text was probably copied, appears to have the same issue but no errata.

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