When should you use Subject line matches approved content?

Run this when the subject is something that had to be approved, and therefore something that can drift. The subject is the one line that has to clear legal, brand and campaign review, and the one most often edited after it did — usually in a hurry, usually by someone who was not in the review. It is also the cleanest gate for AI-generated sends, where a plausible rewrite of an approved line is exactly the failure you cannot spot by reading.

Skip it when there is no approved subject to hold the send against, which is most routine marketing where the subject is written and sent in one motion. It is also not a length check — a subject can be exactly the approved one and still be cut off in the inbox, which is the subject-length check's question. And it cannot judge quality: an approved subject that performs badly passes, because approval is the standard being enforced, not effectiveness.

a subject edited after approval; a required disclosure phrase missing from the subject; prohibited wording reaching the inbox

A failure means the delivered subject is not the approved one, or breaks a rule you set about its contents — a required phrase absent, a prohibited pattern present, or a required shape unmatched. On a regulated send that is a compliance exposure rather than a copy defect, since the subject is frequently the line a disclosure obligation attaches to. In practice the most common cause is an edit made after sign-off, which is precisely the event the check exists to catch.

Four parameters carry the check. `approvedSubjects` defaults to an empty list at `required` severity, which is a deliberate gate: with nothing approved there is nothing to verify, so the check reports as needing configuration rather than passing vacuously. `requiredSubjectPhrases` and `prohibitedSubjectPatterns` are empty by default, adding phrase-level rules only when you set them, and `requiredSubjectPattern` is an optional expression for senders whose subjects must follow a shape rather than an exact wording.

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