PostHog → AI → your inbox. AI drafts the follow-up in your voice; a second AI grades it. What clears your bar sends itself, from your address. A holdout proves what it caused.
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Every workspace starts in dry-run: it drafts for a week and sends nothing until you say go.
To marisol@stoneprint.studio
trigger: workspace.connected · 09:21
Hey Marisol,
Stoneprint just connected a workspace but didn’t get past inviting your teammates. Most folks at this point either hit a snag with SSO or wanted to import their existing brand kit first. Which is it?
Either way I’ll handle it today. Just hit reply.
Best,
Suyash
auto-sent
92%
7 days · 8% you reviewed
trigger fired
09:21user.signed_up
marisol@stoneprint.studio · trial · seats=1
Saw you connected a workspace…
judge: grounded · one ask · safe
Looks like you’re getting your money’s worth
judge: self-corrected ×1, then cleared
welcome flow
measured2.4×
trial-to-paid vs the 10% held back
7.0% emailed · 2.9% held back
replacing streak · lemlist · mailchimp · the shared notion doc
You launched. Two hundred people signed up. You DM'd the first ten, meant to get to the rest, and never did. Fluxway watches your SaaS for the moment that matters, a trial ending, a feature clicked, a payment failing, and writes that 1:1 the second it happens. Every user hears from you, not just the ten you got to.
no templates · no merge tags · written fresh for one person
same trigger · trial.expired
to leo@cypress.app
hey leo, trial's up friday and the deploy hooks never landed. want the three-line fix before it lapses?
to priya@meadow.studio
hi priya, your trial ends friday and the whole team is already in. worth five minutes to set up billing so nobody loses access?
Two people, one moment, two different emails. Never the same paragraph twice.
A second AI grades every draft, in your voice and grounded in your own product so it can't invent a feature or misquote a price, and re-writes the ones that fail. Clear your bar and it sends itself; you get two hours to catch it. You never have to.
tonight's queue · scored by the judge
Over the bar, it sends itself. 2-hour cool-off, then out from your address.
Under it, the draft waits in your queue with the judge's critique attached. Nothing sends without you.
The whole path, from a PostHog event you already track to an email in your voice.
workspace.connectedmatched09:21trial.expired08:47pricing.viewed08:12invite.skipped07:59seat.added07:31+ 32 more today
Events you already send to PostHog, Stripe, or Segment. No new SDK.
“Email founders who connect a workspace but never invite their team.”
Describe the moment in plain English; AI assembles the flow.
To marisol@stoneprint.studio
Saw you connected a workspace
Hey Marisol, you connected a workspace but haven’t invited your team yet. Want a hand getting them in?
Marisol replied · 2:04pm · your inboxinterested
“Yes please, the SSO step is confusing.”
a response is already drafted in your queue; replies never auto-send
Your voice, your address. Replies land in your own thread.
A random 10% of the people a flow matches get held back; conversions are counted from your own PostHog and Stripe events. Run it on any flow: welcome, trial-to-paid, or win-back. Not enough data says not enough data.
2.4×more trials turned paid, against a held-back 10%.
A number you can put in a board deck. Causal, not a vanity open rate.
0 tracking pixels · opens unmeasured, on purpose
got the email
7 in 100 converted
held back
3 in 100 converted
And when the numbers are too small to trust, it says so:not enough data yet
With your consent it reads how you actually write, and every edit you make in the queue teaches it further. Drafts stop sounding like AI and start sounding like you, and the judge holds every send to that voice.
consent-gated · encrypted · one click deletes it
Hi Sarah! I hope this email finds you well. I just wanted to take a moment to check in and see how your trial has been going so far…
Best regards,
Suyash
hey sarah, saw the export fail twice yesterday. what format were you after?
— s
drag → to see what generic ai would have sent
Find the column you live in today. Most founders are in the first one, where the email that would land the upgrade never quite gets sent.
swipe → to read across
| do it yourselfGmail + a sheet | ai inbox assistantFyxer · Serif | lifecycle marketingCustomer.io · Loops | founder follow-upsFluxway | |
|---|---|---|---|---|
| built for | you, in spare minutes | your reply pile | a marketing team | one founder, 1:1 |
| fires on | you remembering | mail that lands first | a schedule you set | a product signal: trial ends, payment fails |
| who writes it | you, at 11pm | AI, in your voice | campaign templates | AI in your voice, no templates |
| quality gate | you re-read it | you approve each one | A/B subject lines | a second AI judges every draft |
| sends from | your address | your address | a brand domain | your address, your threads |
| proof it works | gut feel | none | opens and clicks | lift vs a 10% holdout |
| so it | often never gets sent | waits for them to email you | blasts the same note to everyone | reaches every user, as you, proven |
the rule: 2-hour cool-off, always
Every email waits out a cool-off you can edit, send now, or stop. Pause everything in a click.
the rule: your address, your thread
Your own inbox: Google, Outlook, or IMAP. Replies land in your threads. We never relay through ours.
the rule: capped per workspace
A monthly cap per workspace; drafting pauses at the cap. No overages, no auto-upgrades.
the rule: opens unmeasured, on purpose
Pixels get personal email flagged, and an open was never a result. We measure replies and conversions, against a holdout.
One credit per email, split half on the draft and half on the send. Every plan starts with a 14-day free trial. After that, plan credits refresh monthly and one-time top-ups never expire. Cancel anytime, with no overages and no surprise bills.
Need more before your next cycle? Buy a one-time top-up at any size. Purchased credits roll over and never expire, and bigger plans bring the per-credit price down.
It sends on its own, that's the point. Every draft waits out a 2-hour cool-off in your queue first (adjustable per flow). Open it to edit, send it early, or stop it. Do nothing and it goes out in your voice.
A second, independent AI grades every draft on five named checks: grounded in real activity, your voice, one ask, right length, safe to send. Fail the bar and the writer re-drafts against the judge's critique before you ever see it. It also can't invent product claims; pricing and features must come from facts you've verified. Still wrong? Catch it in the cool-off: open, press S, it's gone. Worst case the user gets no email, no worse than today.
The only honest answer in email: a holdout. Opt a flow in and Fluxway randomly holds back 10% of the people it matches, then counts conversions from your own PostHog and Stripe events for both groups. You see “emailed users converted at 2.4× the holdout” with real confidence intervals, or “not enough data yet,” which no other email tool will ever admit.
Because we don't embed tracking pixels. They're a tell that gets personal email flagged, and an open was never a result. You get the numbers that matter: replies (in your inbox) and conversions (in your PostHog, measured against the holdout). If you need open-rate dashboards, Customer.io will happily sell you one.
Yes. Run any flow in dry-run mode for a week: you'll see every draft that wouldhave sent, with the trigger event and the AI's reasoning. No inbox connection required until you're ready.
Your inbox thread. Always. We send from your address, so when the recipient hits reply it lands in your inbox like any other email, with the full thread context. No relay, no separate dashboard, no notification we forget to send.
Lemlist is for sales teams running outbound at scale. Customer.io is for marketing teams running campaigns. Both blast to lists. Fluxway is the opposite: built for one founder, it drafts and sends in your voice, one user at a time. If you have an SDR team, this isn't for you.
A credit subscription. One credit covers one email: half is charged when the AI writes the draft, half when it sends. Plans start at $20 a month, and every plan begins with a 14-day free trial. Need more before your next cycle? Buy a one-time top-up from $0.20 a credit; those roll over and never expire. Run out and drafting pauses until you top up. No surprise bills, no auto-upgrades, no usage email at 11pm.