What separates an A cold email from a D
Cold emails that get replies share a shape. They are short enough to read on a phone without scrolling, written at a reading level a tired executive can skim, and spend most of their words on the reader rather than the sender. They open with something specific, offer one line of proof, and close with one question that takes a sentence to answer. A D email inverts every one of those: it is long, it talks about the sender's company, it uses a stock opener, and it either buries the ask or asks for too much.
None of this is about cleverness. The reader is deciding, in a few seconds, whether replying is worth the effort and whether the sender did any work. Length, pronoun balance and the position of the ask are measurable proxies for both, which is why a rules-based grader gets surprisingly close to how a human would judge the email.
The 13 checks and the thresholds behind them
The grade starts at 100 and each check deducts points in proportion to how strongly it predicts a skipped email. A is 90 or above, B is 80 to 89, C is 70 to 79, D is 60 to 69, and anything below 60 is an F. The thresholds are opinionated on purpose; they describe the emails that get answered, not the ones that are merely acceptable.
- Length: 50 to 120 words passes. Under 30 or over 160 loses 16 points; in between loses 8.
- Reading level: Flesch-Kincaid grade 8 or below passes. Over 10 loses 12.
- You/me ratio: at least 1.5 second-person words for every first-person word passes. Below 1.0 loses 12.
- Sentence length: 16 words or fewer on average passes. Over 22 loses 10.
- Questions: one or two passes. None, or three or more, loses 6.
- Links: zero or one passes. Three or more loses 12.
- Call to action: a recognizable ask (call, chat, reply, open to, worth, minutes, or a question) must exist, or 12 points are lost.
- Mobile fold: the ask should start within the first 300 characters, or 5 points are lost.
- Opener clichés lose 8, spam triggers lose 6 to 14, more than four paragraphs lose 4 to 8, a subject over 50 characters loses 4.
The you/me ratio, reading level and the mobile fold
The you/me ratio counts "you" and "your" against "I", "we", "our" and "my". Most first drafts come in below 1.0 because they describe the product. Flipping sentences to start with the reader's company or problem usually moves the ratio past 1.5 without changing the facts. Reading level uses the Flesch-Kincaid grade formula: 0.39 times words per sentence, plus 11.8 times syllables per word, minus 15.59. Grade 8 is roughly a newspaper. Long words and long sentences push the grade up; short ones bring it down.
The mobile fold is the amount of body text visible on a phone before the reader scrolls, which is about 300 characters once the subject and sender take their share of the screen. If your ask sits at character 600, the reader has to decide to keep going before they even know what you want. The first-screen preview in the results panel shows exactly where that cut lands so you can move the question up or delete what comes before it.
How to turn a C into an A in three edits
Start with the opener. Delete anything that could open an email to anyone: "hope this finds you well", "my name is", "I'm reaching out". Replace it with one sentence about something you noticed, such as a hire, a launch, a pricing change or a job post. Second, cut the paragraph about your company. Keep one line of proof, ideally a similar company and a specific outcome, and remove adjectives like "leading" and "world-class", which are spam triggers as well as filler.
Third, rewrite the ask. One question, low effort, visible before the scroll: "Worth a 15-minute call next week?" or "Open to me sending the two-line version?" Do not offer a demo, a deck and a call in the same sentence. After those three edits most emails land at 80 or above; the remaining points usually come from splitting long sentences. The AI grader reads for what rules cannot, such as whether the proof is relevant to that reader, and returns a rewrite. ColdBox runs the same grade on every step of a sequence before it goes live, and a second time whenever you edit it.