Keep Your SMS in the Known Sender Inbox with Onsite Opt-in Engage

With Apple’s iOS 26 update making it easier to activate the Screen Unknown Senders filter, keeping your brand in the Known Sender inbox is more important than ever.

That’s why we built Onsite Opt-in Engage, a patent-pending new enhancement to Postscript’s patented Onsite Opt-in flow. It gives your subscribers a seamless way to confirm their subscription and send an initial message to your brand, locking in Known Sender status from day one, whether they opt-in on desktop or mobile.

Apple’s inbox filter creates a simple but potentially high-stakes divide: Known Senders get the main inbox, Unknown Senders become less visible. For SMS marketers, that means if you’re not in the right inbox, your carefully built subscriber list may not pay off at its full value.

While other options to get into the Known Sender inbox exist, they’re either built on clunky legacy tech, require manual work like saving a number, or can’t even get your first message into the known inbox. And none of them are as powerful as converting visitors into SMS subscribers as Onsite Opt-in. Not exactly a recipe for scale.

We designed Onsite Opt-in Engage to automate this moment of subscriber connection, giving brands a frictionless way to ensure they’re showing up in the right inbox from the very first send.

The Onsite Opt-in Engage flow is simple, fast, and fully compliant:

For mobile:

1. Subscriber enters their phone number in your popup.

2. Postscript sends a one-time passcode (OTP) from a Postscript-owned number. This keeps your brand’s number eligible for Known Sender placement.

3. Subscriber enters the OTP to verify their subscription.

4. They’re then taken to their messaging app with a pre-populated message ready to send to your brand.

5. They hit send. That subscriber-initiated conversation instantly helps your brand qualify as a Known Sender.

For desktop:

1. Subscriber enters their phone number in your popup.

2. Postscript sends a one-time passcode (OTP) from a Postscript-owned number. This keeps your brand’s number eligible for Known Sender placement.

3. Subscriber enters the OTP to verify their subscription.

4. They’re then shown an additional step with a QR code linking to their messaging app with a pre-populated message ready to send to your brand.

5. They hit send. That subscriber-initiated conversation instantly helps your brand qualify as a Known Sender.

The result: No trade-off on opt-in performance, stronger connections, and better visibility on every message that follows.

Plenty of opt-in methods exist, but none were purpose-built for the Known Sender era. Here’s what sets Onsite Opt-in Engage apart:

• Built for compliance and deliverability. Onsite Opt-in Engage layers on top of our patented Onsite Opt-in technology that utilizes familiar OTPs, ensuring every subscriber is verified and ready to receive.

• Subscriber-first experience. The flow feels natural, intuitive, and quick, no clunky opt-in methods compromising your list growth rate.

• The first desktop opt-in method to solve for message filtering. Until now, desktop opt-ins had no clean way to land in the known inbox from the jump.

• Future-proof by design. As Apple continues to evolve SMS filtering, Postscript is proactively innovating to keep your brand ahead of the curve.

Onsite Opt-in Engage is in Beta today for Postscript merchants. It’s especially impactful for:

• Brands on Shopify who are doing $2M to $100M+ in revenue per year where list growth is critical and any dip can cost millions in lost revenue.

• Brands heading into BFCM looking to safeguard the reach of their biggest campaigns.

• Merchants with high traffic who need a smooth, trustworthy opt-in flow on both mobile and desktop.

With Onsite Opt-in Engage, brands can:

• Protect inbox placement from the very first subscriber interaction.

• Build more trusted, lasting subscriber relationships.

• Boost campaign performance and revenue by ensuring your messages are actually seen.

Or put simply: your popups won’t just capture more subscribers, they set you up for better visibility and more revenue.

If you’re considering holding off until this has unfolded a bit more, that’s fair. Apple has not released data on how many people will update to iOS 26 right away, nor how many will actually enable Screen Unknown Senders. Adoption will likely take time, and not everybody will enable this feature. 

But if you would rather not risk any changes to deliverability, especially heading into BFCM, Onsite Opt-in Engage is available in beta now. Turning it on means your brand will be proactively covered for Known Sender inbox placement.

Turning on Onsite Opt-in Engage takes minutes. You’ll keep growing your list at the highest possible rates while ensuring your messages are reaching the Known Sender inbox.

Want in on the beta? Fill out this form to get access.