FA-76829 / Email MIME structure / Member archive

Decide whether a message is interpreted as MIME: first version wins · case 04

A later MIME-Version header overrides an empty first one and turns a legacy message into MIME.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

headers are [name, value] pairs with case-insensitive, trimmed names; the first occurrence of MIME-Version and of Content-Type is used. The MIME-Version value, after removing parenthesised comments and all whitespace, must equal "1.0"; otherwise the message is ["text/plain", "non-mime"]. MIME messages report [type, "mime"] with the type taken from the first Content-Type (before ";", trimmed, lower-cased; text/plain when absent or empty).

Why this case matters

Legacy messages without MIME-Version must not have their Content-Type honoured.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
empty first version header	`["text/html", "mime"]`	`["text/plain", "non-mime"]`	Failed

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