Deliverability is the share of the messages you send that actually reach a phone, as opposed to being filtered, blocked or silently dropped on the way. It is decided less by the network than by the paperwork: whether the sender is registered, how the brand was scored, which carriers the provider connects to directly, and what happens when a phone cannot take the message format you sent.
What moves it
Four things account for most deliverability problems in US business messaging. Unregistered or under-registered A2P traffic on a 10-digit number, which carriers filter as suspected spam. A low trust score that throttles throughput below the volume you are sending. Content that trips carrier filters, such as public URL shorteners or prohibited categories. And the absence of a fallback path, so that a rich message to a phone that cannot render it is lost rather than downgraded.
Deliverability on RCS
RCS adds two mechanisms SMS lacks. A capability check before sending tells the platform whether the handset can receive RCS, and automatic fallback to SMS carries the message anyway when it cannot. Delivery and read receipts then report what happened per message, so a deliverability problem is diagnosable rather than inferred from silence.
Measuring it
Track delivered rate by carrier and by number type, and watch for a sudden drop, which almost always means a registration or filtering event rather than a network fault. RCS messaging blocked walks through the usual causes.