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Inbound SMS arrives on the Twilio webhook for each connected number. The handler:
  1. Looks up the Channel for the destination number.
  2. Searches for an open Conversation that includes the sender’s phone number.
  3. Creates a new Conversation if none exists, linking it to any records whose phone property matches the sender.
  4. Applies the channel’s routing rules to assign the message to a user (or queue).

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Routing rules

Channel routing rules are evaluated top-down on every inbound message. A rule can match by content keyword, sender area code, time-of-day, or record property. The first matching rule wins. If no rule matches, the channel’s default assignment applies.

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Opt-out keywords

STOP, UNSUBSCRIBE, END, CANCEL, QUIT, and the Spanish equivalents are intercepted by Twilio at the carrier level. These never reach Custral. The number is added to your Twilio account’s opt-out list automatically.