Founder-led SaaS onboarding over iMessage

Who uses iMessage for SaaS onboarding?

Founder-led onboarding over iMessage suits early-stage B2B SaaS and product-led tools where activation matters more than raw signups and the founder still talks to new users. ZeroSettle is an iMessage API: a real phone number on real iMessage, running on Apple hardware we operate for you, that your code texts customers from and hears back on through a bearer token and signed webhooks.

It targets the trial that dies at step two: a user signs up, stalls at the import or the first integration, and quietly leaves. An onboarding email is easy to skip, and in-app chat only reaches them while they are in the app. Related jobs have their own pages: for the end of a trial, trial-ending reminders and a "text the founder" step in the cancel flow; for sales-led signups, an AI SDR for demo requests. More are on the use-case hub.

How iMessage for SaaS onboarding works, step by step

Your signup form collects an opt-in, your backend sends the founder's question through ZeroSettle, the founder answers from the console, and a stall in your analytics triggers at most one nudge in the same thread.

1. Ask at signup. Add an optional phone field with an unchecked box: "Want a text if you get stuck? The founder may text you to help you set up." Store the wording and when it was ticked.
2. Put the founder on the card. Set the line's name, such as "Nina from Tallyroom" (up to 64 characters), and a square JPEG or PNG of the founder under 3 MB with PUT /api/imessage/profile or in the console. ZeroSettle shares the card with each first message; what the user sees depends on their device and contact settings.
3. Send one question with POST /api/imessage/send, and no link: an iPhone shows a link from an unknown sender as plain text until the user replies or saves the number. See how to write a first iMessage people reply to.
4. The founder answers in the ZeroSettle console. Each reply also reaches your webhook as a signed message.received event about 1–2 seconds after it lands.
5. Nudge on a stall. When analytics show "import started 24 hours ago, never finished" or "no integration by day 3", send one nudge into the same thread. It is not a new contact.
6. Show, don't link. Once the user has replied, answer with a screenshot (image_b64, up to 5 MB, caption in the same bubble) or a 20-second voice note (audio_b64, up to 6 MB, arriving with a waveform and the transcript the user's phone generates) rather than a help-doc link. Photos and voice notes go only to users who have replied (until then ZeroSettle returns 403 attachment_before_reply), and a settings link shows as plain text until then too, so a nudge to a silent user is a short text.

Or let the user text first

The welcome screen can offer your ZeroSettle number as an sms: link with "Hi Nina" prefilled. A user who texts first is never a new contact, links work at once, and the thread avoids iOS 26's Screen Unknown Senders list, which Apple turns on at upgrade for anyone who had Filter Unknown Senders on in iOS 18. On Android the link opens SMS, so keep email as the fallback (more on getting customers to text first).

Example conversation: SaaS onboarding

Here the welcome question gets a reply naming the blocker, and one screenshot from the founder clears it the same morning.

Setup: a signup opt-in and analytics-triggered nudges

One small service covers it: welcome() for your signup handler, nudge() for your stall job, and a webhook that verifies ZeroSettle's signature and records who replied. It follows the docs on sending and webhooks.

# onboarding.py: run with  uvicorn onboarding:app --port 8100
import base64, hashlib, hmac, json, os, time
import requests
from fastapi import FastAPI, Request, Response

BASE = os.environ.get("ZEROSETTLE_BASE_URL", "https://portal.zerosettle.io")
TOKEN, SECRET = os.environ["ZEROSETTLE_TOKEN"], os.environ["ZEROSETTLE_WEBHOOK_SECRET"]
app = FastAPI()

# Yours to write. Store user.phone in E.164 (+1...) so it matches the webhook's handle.
def queue_welcome(user, after_s: int) -> None: ...  # welcome(user, queued=True), never at night
def mark_replied(handle: str) -> None: ...          # set replied_at for that phone; idempotent

def send(to: str, **fields) -> dict:
    return requests.post(f"{BASE}/api/imessage/send", json={"to": to, **fields},
                         headers={"Authorization": f"Bearer {TOKEN}"}, timeout=120).json()

# Run from one background worker after signup, only if the box was ticked:
# each send waits until it is handed to Apple, and sends go one at a time per line.
def welcome(user, queued: bool = False) -> None:
    if queued and user.activated:              # they got going without help
        return
    when = "recently" if queued else "today"
    r = send(user.phone, text=f"Hey {user.first_name}, Nina here, I built Tallyroom. "
                              f"Saw you signed up {when}. What are you hoping to automate first?")
    err = r.get("error") or {}
    if err.get("code") == "new_contact_limit":  # the day resets at 3 AM Eastern
        queue_welcome(user, after_s=err["retry_after_s"])

def nudge(user) -> None:                       # your stall job calls this once per user
    caption = "Nina again. Imports usually stall on the sandbox toggle: set it to Production and retry."
    if not user.replied_at:                    # photos and links wait for a reply
        send(user.phone, text=caption)
        return
    caption += " https://app.tallyroom.example/settings/integrations"
    with open("shots/import-toggle.png", "rb") as f:
        png = base64.b64encode(f.read()).decode()
    send(user.phone, image_b64=png, image_format="png", text=caption)

def verify(secret: str, header: str, raw_body: bytes, tolerance: int = 300) -> bool:
    try:
        parts = dict(p.split("=", 1) for p in header.split(","))
        t, v1 = int(parts["t"]), parts["v1"]
    except Exception:
        return False
    if abs(time.time() - t) > tolerance:
        return False
    expected = hmac.new(secret.encode(), f"{t}.".encode() + raw_body, hashlib.sha256).hexdigest()
    return hmac.compare_digest(expected, v1)

@app.post("/webhook")
async def webhook(request: Request):
    raw = await request.body()
    if not verify(SECRET, request.headers.get("X-ZeroSettle-Signature", ""), raw):
        return Response(status_code=401)
    payload = json.loads(raw)
    if payload["event"] == "message.received":  # your own sends echo back as message.sent
        mark_replied(payload["message"]["handle"])   # retries repeat it harmlessly
    return Response(status_code=200)

Register the receiver with PUT /api/imessage/webhook and store the secret; it is shown once. A voice note sends audio_b64 (m4a, mp3, wav and more) with no text. Keep screenshots within 2048 px on the long edge: a PNG or JPEG that size goes out exactly as sent, while anything larger is re-encoded to JPEG (which also strips EXIF and GPS).

Limits and consent for SaaS onboarding

Each opted-in signup uses one new contact, for the founder's question; nudges and replies in that thread use none. On Pro that means 5 welcomes a day per number, about 150 a month at an even pace.

Source: ZeroSettle iMessage API docs, "Errors, limits, and compliance". Anyone who texted the line first is never limited.

Launch-day math

Suppose launch day brings 200 signups and 120 tick the box. On Pro, 5 welcomes go out that day; the other 115 sends return 429 new_contact_limit with retry_after_s, and at 5 a day the last would wait more than three weeks. Re-check activation before each queued welcome, drop "today" from the wording, and hold any that would land at night, since the day resets at 3 AM Eastern. For a user facing a wait of several days, your onboarding email is the better first touch, and a launch this size is a reason to book a demo for Growth.

On Growth with three numbers (150 a day, 9 per 15 minutes), all 120 go out in about three and a quarter hours. But a silent user's welcome plus one nudge a day or more later uses the 2 unanswered messages every plan allows (only messages within 5 minutes of each other count as one), so a second nudge returns 403 awaiting_reply.

When ZeroSettle is not a fit for SaaS onboarding

ZeroSettle is the wrong tool for onboarding texts when:

• Opted-in signups exceed about 5 a day on one number and you won't move to Growth. The rest wait days for a signup-day welcome.
• You want sales pressure. Upgrade pushes need marketing consent, and ZeroSettle suspends lines used for unsolicited messaging.
• Your users rarely carry iPhones, such as an Android-heavy or desktop-only audience. SMS fallback is only on ZeroSettle's roadmap. ZeroSettle does check each first message with Apple: a number not on iMessage gets 422 not_on_imessage, nothing is sent and no new contact is used.
• You need in-app guided tours. That is a different tool; ZeroSettle carries messages outside your app, not walkthroughs inside it.

How much does iMessage for SaaS onboarding cost?

Onboarding texts cost the plan price: ZeroSettle has no per-message fees, and messages are unlimited (counted).

Neither plan has a setup fee, and the subscription carries a 30-day money-back guarantee. AI credits (1,000 a month on Pro, 5,000 on Growth) are only for the hosted AI agent; welcomes, nudges and the founder's answers use none. See pricing, get a Pro number, or book a Growth demo.