Understanding Unknown Senders filtering on iOS and how it affects RCS

Understanding Unknown Senders filtering on iOS and how it affects RCS

Estimated 3 minute read

Updated Feb 24, 2026, 12:00 AM EST

Table of contents

How the Unknown Senders inbox works
Contact Cards
Recommended best practices
Summary

When you send RCS messages, they are delivered from an RCS agent. If you've sent SMS messages previously, then your subscribers will be receiving your RCS messages from a new sender. Although these messages are sent from your branded and verified RCS agent, they may appear in the “Unknown Senders” inbox on some subscribers’ iOS devices.

How the Unknown Senders inbox works

On iOS, users can enable a setting called Filter Unknown Senders (called Screen Unknown Senders in iOS 26), which separates messages from numbers or senders not saved in their contacts and with whom they have not previously engaged.

This setting is off by default, meaning most users will receive all messages in their primary inbox.
When on, the first message from a new Sender ID (e.g. RCS agent) appears in both the primary and unknown senders inboxes, allowing the recipient to review it and mark the sender as known.
If the recipient marks the sender as known, all future messages from that Sender ID (e.g. RCS agent) will appear in the primary inbox.
If they do not, any future messages from that Sender ID (e.g. RCS agent) will appear only in the unknown senders inbox.

Contact Cards

Unlike SMS senders, RCS agents cannot be saved as contacts on a user’s device. As a result, contact cards are not supported on RCS.

If any of your existing flows include contact cards, they will be automatically removed from the RCS version of the message to avoid delivery issues.

If you want to keep a contact card and separate wording in the SMS/MMS fallback, open SMS fallback in the message editor and turn off Use the same content from RCS message before editing the RCS version. When this setting is on, RCS content changes are also copied to the fallback.

You should update these flows by either:

Editing the RCS version of the message to remove references to saving the sender as a contact and instead ask users to mark the sender as known. Review the RCS message and SMS fallback, then click Next to save and return to the flow.
Using a conditional split based on the RCS capability property to route RCS-capable subscribers around the contact-card message.

Recommended best practices

To maximize visibility and keep your RCS messages in the primary inbox, encourage recipients to mark the sender as known when making first contact on an RCS agent.

For instructions you can share with subscribers, see Apple’s guide to reviewing unknown messages and marking senders as known.

Summary

RCS messages are sent from a new Sender ID (RCS agent).
RCS agents cannot be saved as contacts, and contact cards are not supported on RCS.
The Unknown Senders filter is off by default. When enabled, messages from unknown senders, including RCS agents, are moved to the Unknown Senders inbox.
When someone receives a message from an RCS agent for the first time, they are prompted to mark the sender as known. Once marked as known, all future messages from that RCS agent will appear in the primary inbox.

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