Keep or delete exactly one soft-break space
02DelSp tells a reader whether the SPACE immediately before a soft CRLF is content or an extra marker to remove.
Separate received example: DelSp=unknown means No. With two trailing spaces both remain; the reader must not silently guess Yes or trim all whitespace.
Source for this drawing: RFC 3676 · Read RFC section 4.2 ↗
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Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
RFC3676 obsoletes RFC2646 and adds DelSp for natural wrap points without existing ASCII spaces. The older method remains supported.
Read the updated RFC section ↗DelSp=yes deletes one marker, not every trailing space.
- The older generation method inserts CRLF after an existing space. DelSp SHOULD be specified and, if present, MUST be no for that method.
- The newer method inserts SPACE plus CRLF at a natural wrapping point. It MUST specify DelSp=yes. When a content space already exists, inserting the marker after it is RECOMMENDED.
- Missing or unrecognized DelSp defaults to No. DelSp without Format=Flowed has undefined use; receivers SHOULD ignore it outside Text/Plain; Format=Flowed.
All examples use an existing inter-word space. The yes example has TWO trailing spaces: one content space plus one added marker. The new technique also supports natural boundaries in languages that rarely use ASCII spaces; it does not recommend splitting ordinary English words. Generated lines SHOULD be at most 78 characters including stuffing and trailing spaces, excluding CRLF; an overlong word is a stated exception. Older flowed clients unaware of DelSp can retain an extra space. Quoted-Printable SHOULD NOT be used unless needed, with the signed/encrypted exception discussed in section4.2.
Read the RFC section ↗