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Line type and reachability classification model

A line type tells you what a number can do, not whether a message to it was delivered. This page is the model for reading that signal: which of Orbit’s three classification surfaces answers your question, what the per-channel reachability verdict actually means, and where an operator wires classification into tenant-owned posture — quiet-hours windows, the Reassigned Numbers Database (RND) scrub, and opt-out lists. For the dip-level fields of the billed lookup, see the Number Lookup model.

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The three classification surfaces

Orbit classifies numbers and sender identities on three surfaces, in order from cheapest to most authoritative: Use the public checker in pre-purchase flows and triage — an anonymous visitor can validate and classify a number without consuming lookup credits. Behind it sits the same structural E.164 validator the platform’s format helpers use, so the checker never disagrees with the API about whether the input is a complete, dialable number. Run the billed Lookup when you need a live network answer (list hygiene at import time, pre-screens before high-risk sends, the Numbers → Lookup console desk-check flow). The sender-identity-type resolver runs whenever you list senders — the compliance surfaces render “Long code” / “Toll-free” / “Short code” / “Alphanumeric sender ID” instead of lumping every from identity under “Number”.

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How classification feeds tenant posture

Sender-identity classification is what makes the compliance profile’s pre-send evaluation readable: in the Messaging Compliance Health panel each sender row rests under its true identity class, so a screened quarantine on one class (e.g. unverified alphanumeric) can be read without mislabeling phone numbers as non-numeric senders. The send gate evaluation itself — quiet hours, DNC, RND, preference checks — is documented under Send Gates; the identity resolver ensures the sender shown in those gate decisions is labeled correctly. Ownership stays with the tenant: except for the sole platform-global federal TCPA dialing window, every posture check is a tenant-configured control. Billed lookups feed list hygiene. A typical flow: run a bulk Lookup on newly imported numbers, filter for lineStatus !== active or a fixed line / premium rate / shared cost type, and route the misses into your opt-out list or a suppression import before a campaign touches them. The checker is the free first-pass of that same triage; the Lookup is the authoritative second pass you pay per dip.

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Reading the reachability verdict

The public checker resolves a line type from the numbering plan and maps it to a general reachability verdict per channel: An incomplete input or an invalid number resolves depends on both channels with a note that says why it couldn’t classify. Per channel, the verdict stacks like this:
  • SMS — a yes means the numbering category supports A2P/P2P SMS; a depends means the category supports SMS for some provisioned instances (fixed-or-mobile ranges, toll-free after verification, VoIP with a provider add-on); a no means the category is not an SMS endpoint.
  • Voice — nearly every reachable numbering category terminates a call; no is reserved for pager and voicemail-access ranges.
  • RCS and WhatsApp — neither gets a separate verdict. Both inherit the SMS constraint: you need an SMS-capable destination before the richer channel can even attempt a capability fall-back. WhatsApp registration materially narrows to mobile lines, and RCS delivery mirrors SMS’s reachability — treat a fixed-line-type no for SMS as a matched no for RCS/WhatsApp, and upgrade a depends only after a SMS test confirms the line. Where WhatsApp adds no business-voice fallback, see the WhatsApp Business Calling model.

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When a lookup answers “depends”

A depends verdict is not a shrug — it is the honest answer for a category where the provisioned instance, not the numbering plan, decides reachability. In a BYO-carrier agreement the classification still holds (the number’s plan-derived type doesn’t change when you attach carrier credentials), but who provisions SMS on a VoIP or fixed-or-mobile range does change. The BYO carrier lifecycle page covers how attaching your own SMPP carrier shifts reachability from market-average empirics to your own bind’s capability. Operators should treat BYO ranges classified depends as candidates for a binding-capability test message rather than as excluded destinations. The billed Lookup narrows depends further: HLR returns the current serving carrier and the tri-state lineStatus, so a tentative checker verdict resolves to a live one at send-decision time. Where depends stays unresolved — especially on VoIP — the safe posture is tenant-owned suppression (move the number off your send lists until a test message or the subscriber’s own choice settles it), not an optimistic send.
  • Compliance country requirements — sender-ID restrictions that vary by country. The line-type verdict does not override these: an SMS-yes mobile number still hits the country’s sender-class rules before a send dispatches.
  • Send Gates — the quiet-hours / DNC / RND / preference evaluations that run at send time; line-type signals choose which channels are worth attempting, the gates choose whether a send runs.
  • BYO carrier lifecycle — how attaching your own carrier changes what a depends verdict means.
  • Number Lookup model — the dip catalog behind the billed endpoint and how its cache trades freshness against cost.
  • Number Intelligence dashboard — the console, metering, and daily-cap surfaces for operator-side lookups.
  • Opt-out lists — where filtered-out numbers land when classification says “not an SMS endpoint”.