{"id":2949,"date":"2026-09-07T11:27:10","date_gmt":"2026-09-07T05:57:10","guid":{"rendered":"https:\/\/www.smsgatewaycenter.com\/blog\/?p=2949"},"modified":"2026-09-07T11:27:12","modified_gmt":"2026-09-07T05:57:12","slug":"contact-groups-segments-data-model-group-send","status":"publish","type":"post","link":"https:\/\/www.smsgatewaycenter.com\/blog\/contact-groups-segments-data-model-group-send\/","title":{"rendered":"Contact Groups and Segments: The Data Model Behind a Group Send"},"content":{"rendered":"\n

A group send names a list, not a set of people. This is the engineering guide to what a contact group actually is on SMSGatewayCenter, how the eight group and contact endpoints fit together, why success is not always code 200, and how to keep your own contact system in sync with a list your code cannot enumerate.<\/p>\n\n\n\n

\"Geometric<\/a>
A group send addresses a container, not the people inside it. The individual records only appear afterwards, in the delivery report feed.<\/figcaption><\/figure>\n\n\n\n

Table of Contents<\/h1>\n\n\n\n
    \n
  1. The Short Answer<\/a><\/li>\n\n\n\n
  2. TL;DR<\/a><\/li>\n\n\n\n
  3. What a Group Actually Is on This Platform<\/a><\/li>\n\n\n\n
  4. The Eight Endpoints and What Each One Can Address<\/a><\/li>\n\n\n\n
  5. One Group, Five Spellings of Its Identifier<\/a><\/li>\n\n\n\n
  6. Success Is Not Code 200<\/a><\/li>\n\n\n\n
  7. One Contact, One Group<\/a><\/li>\n\n\n\n
  8. Enumerating a Group With an Endpoint That Has No Filter<\/a><\/li>\n\n\n\n
  9. The Group Send Blind Spot<\/a><\/li>\n\n\n\n
  10. The Send Response Union Is Now Complete<\/a><\/li>\n\n\n\n
  11. Overlapping Groups and duplicatecheck<\/a><\/li>\n\n\n\n
  12. When Does Membership Resolve<\/a><\/li>\n\n\n\n
  13. Keeping Two Contact Systems in Sync<\/a><\/li>\n\n\n\n
  14. Consent, DND and DLT for a List You Cannot Enumerate<\/a><\/li>\n\n\n\n
  15. The Sync and Audit Playbook<\/a><\/li>\n\n\n\n
  16. A Schema That Survives All of This<\/a><\/li>\n\n\n\n
  17. Ten Mistakes That Cost Real Money<\/a><\/li>\n\n\n\n
  18. Decision Matrix: Platform Groups, Your Own Lists, or Both<\/a><\/li>\n\n\n\n
  19. Build Order<\/a><\/li>\n\n\n\n
  20. The Checklist<\/a><\/li>\n\n\n\n
  21. Unspecified Behaviour and How to Code Around It<\/a><\/li>\n\n\n\n
  22. FAQs<\/a><\/li>\n<\/ol>\n\n\n\n

    <\/p>\n\n\n\n

    The Short Answer<\/h2>\n\n\n\n

    A contact group on SMSGatewayCenter is a server-side list identified by a numeric groupId<\/code>, and when you send to it with sendMethod=group<\/code> the API returns the group identifier and a transaction identifier but no recipient information at all. There is no mobile<\/code> field and no invalidMobile<\/code> field in that response. Your application therefore cannot know, at submission time, who it just messaged. The only place individual recipients ever appear is the delivery report feed. That single fact drives everything else in this article: your contact model has to be authoritative on your side, the platform group has to be treated as a projection of it, and delivery report ingestion has to be promoted from monitoring to system of record.<\/p>\n\n\n\n

    TL;DR<\/h2>\n\n\n\n