Every message needs a valid carrier message-class tag

The requirementstatement

Every 10DLC A2P message must carry a valid, authorised carrier message class tag.

Severityseverity: BlockingBLOCKINGBreaking this rule gets the submission rejected. There is no partial credit.
When it bitesphase: After you are livepostFalls due once you are sending: STOP handling, quiet hours, suppression, record retention.
What is checkedobject: outbound message class tag
Where it liveslayer: OperationalOPERATIONAL
How Ekas settles itdetectability: Post-submissionUNDETECTABLE_PRE_SUBMISSION; The subject does not exist yet at submission time: a reply window, an expiring PIN, a queue position. Reported with its deadline.
What the fix involvesfailureClass: Wait on someone elseTERMINAL_EXTERNAL; Needs an external system or a waiting period, such as IRS propagation, a vetting result, or a carrier queue.
Who requires itauthorities: AT&TTelnyx
When it appliesapplicabilityText: Applies to every 10DLC registration.

Why this rule existsrationale

The class tag is how AT&T decides what throughput the message gets and whether it is carried at all, and it is assigned to the campaign rather than chosen per send — so traffic sent with the wrong tag, or none, fails in a way that looks like a throughput problem rather than a tagging one. It is set by the platform, which is why the sender rarely knows it exists until delivery is unexplainably poor.

How to fix itremediation

Confirm with your provider which class the campaign was assigned and that outbound traffic carries it. Done when you can state your campaign's message class and it matches what the provider registered.

Check this yourselfattestation

No tool can settle this one for you. Here is the check, and what wrong looks like.

Can you state your campaign's carrier message class, and does the outbound traffic carry it?

1Look the class up in the campaign record at your provider — it is assigned to the campaign, not chosen per send.
2Confirm with them that outbound traffic carries it.
3Mismatches are diagnosed there rather than in any error code.

What wrong looks like: The wrong tag, or none, fails in a way that looks like a throughput problem rather than a tagging one — and it is set by the platform, so the sender rarely knows it exists until delivery is unexplainably poor.

Notesnotes

Applied in the sending path. What the user has to do is ask — the class is visible in the campaign record at the provider, and mismatches between the assigned class and the traffic are diagnosed there rather than in any error code.

Rules you will hit next

Other operational rules at the same severity. A registration is judged as a whole, not rule by rule.

OPS-026The universal opt-out keyword set must be declaredBlockingBLOCKING OPS-027Opt-out keyword handling must be declared, not assumedBlockingBLOCKING OPS-029A revocation must survive punctuation, case and surrounding wordsBlockingBLOCKING OPS-031A plainly-worded opt-out counts even with no keyword in itBlockingBLOCKING OPS-033STOP must never come back as an errorBlockingBLOCKING OPS-037On a shared address, STOP must stop everythingBlockingBLOCKING

All operational rules

OPS-123 is one of 139 operational rules in the 915-rule 10DLC registry. Free to cite under CC BY 4.0.