All packsTransactional Email Deliverability CoreSolve
new domain email warmup sending limits reputation
Full volume from day one gets a fresh domain flagged
Sending at full volume from a brand-new domain gets it flagged as spam before a human notices -- the pack ramps a daily cap over 45 days instead.
This is one of the things Transactional Email Deliverability Core already handles. Send transactional email that actually lands, and stop emailing people who bounce or complain.
Is this you?
A fresh sending domain has no reputation with mailbox providers yet, and sending at whatever volume the app naturally produces -- welcome emails, password resets, receipts, all at once for an existing user base -- reads to spam filters as exactly the pattern a spammer's new domain would produce. The domain gets flagged or throttled by receiving mail servers before anyone building the app notices anything is wrong.
Why this one is easy to get wrong
"Send the email when the event happens" is the entire scope of what an agent is usually asked to build (add password-reset email, add welcome email), and nothing about that task description mentions domain age or sending reputation -- ramping volume over weeks is a deliverability-specific practice that has to be designed in deliberately, not something that falls out of implementing the send logic correctly.
What you get instead
The warmup governor is a pure function, dailyCap(dayNumber), ramping from 20/day in the first three days up to unlimited at day 45 -- checkWarmup() enforces it before every send, and a send that would exceed the day's cap is deferred (recorded, replayable) rather than dropped or blasted anyway. The ramp table itself is a documented reputation-safety policy, not a technical limit that can be safely skipped.
Source: ARCHITECTURE.md 'Warmup governor' — checkable in the pack you receive
How you actually use this
You don’t install a library or wire up an SDK. Your own coding agent builds the code in your project, and you keep it — no runtime dependency on us.
Step 1
Download and unzip
You get a folder: the docs that tell an agent what to build, a starting skeleton, and the test suite that decides when it's done.
Step 2
Open it in Claude Code or Cursor
Point your coding agent at the folder. Nothing to install, no account with us, no API key.
Step 3
Paste one prompt
The pack contains the exact prompt. Paste it as your first message and leave it alone — it works through the build itself, choosing a cheaper or stronger model per task.
Step 4
Run ./verify.sh
One command. It prints a pass or fail for every check. Green means the build is done — the same script we ran to produce the receipt on this page.
Typical build: about 13 minutes of your agent working, mostly unattended. Then you integrate the working module into your app the way you would any code you’d written yourself.
Why you can believe this
3 of 3 runs passedWe ran this pack from an empty folder 3 times and published exactly what happened — every check, the model, the token cost, the wall time. Not a testimonial, and not our opinion: the same verify.sh you run yourself. Read the full receipt →