Every artifact here was built because we needed it ourselves, and every one ships with the suite that keeps it honest. Not a boilerplate scraped together for sale, and not a tutorial with a price on it.
$49 each, one-time · Full source · Commercial licence
Each one names the failures its tests cover. If the list doesn't describe a problem you have, don't buy it.
A cold-email sequencer that is safe to leave running. Warmup ramp, threaded follow-ups, any reply ends the sequence, permanent suppression re-checked before every send, RFC 8058 one-click unsubscribe, crash-safe sent log. Sends through your own AWS SES or SMTP — no SaaS, no per-contact pricing.
openpyxl writes formulas but never evaluates them, so a generated workbook can build cleanly and be arithmetically wrong. xlcheck recalculates it the way Excel would and asserts every figure against hand-computed arithmetic — plus a sweep for error cells you didn't know to look for.
Anyone can publish a script. The reason to pay $49 rather than spend an afternoon writing your own is that the afternoon is not where the cost is — the cost is in the third week, when the follow-up that didn't thread reads as a fresh cold email, or the generated report shows a customer a number that is quietly wrong.
So each product's page names the specific failures its tests cover, in the words of the failure rather than the feature. If that list doesn't describe a problem you have, don't buy it.
Both artifacts above are on sale now — buy either one and the download is instant. This form is for the thing that isn't here yet: tell us which of the two comes closest, and what you'd actually want built, and it goes on the list.