My API call returns success but the SMS never arrives — why?

A success on submission only means the gateway accepted the message. The handset outcome comes later in the DLR, and a submitted message can still fail at the operator for an unregistered sender ID, an invalid number, or grey-route filtering. Read the DLR, not the submit response.

Does an invalid or ported number count against my delivery rate?

Yes. Sending to disconnected, invalid, or out-of-coverage numbers produces failures that lower your delivery ratio and cost you money. Run an HLR lookup first to drop them before you send.

Why do messages deliver in one country but not another?

Delivery is operator- and market-specific. A route that's direct in one country may be grey (and firewall-filtered) in another, and some regulators require a registered sender ID per market. Confirm each destination is on a direct route with a registered ID.

Operations BroadNet answer

Why are my SMS messages not being delivered?

Last reviewed July 31, 20261 min readReviewed by BroadNet engineering

Quick answer

Undelivered SMS almost always trace to one of a few causes — an unregistered sender ID, an invalid or unreachable number, grey-route filtering, wrong encoding, or a handset that is off — and each shows up differently in the delivery receipt.

Plain-language definitionVendor-neutralReviewed July 31, 2026

DiagramHow an A2P message reaches the phone

Your applicationSends over the REST API or SMPP
BroadNet platformValidates, routes and bills each message
Operator SMSCDirect operator connection
Subscriber handsetThe message is delivered

The delivery receipt (DLR) travels back along the same path to your webhook

The long answer

Everything worth knowing, nothing that isn't.

§01

Sender ID not registered

In regulated markets the operator drops A2P traffic from sender IDs that aren't on the registry. The DLR typically reads as rejected. Registering the ID in that market clears the block.

§02

Invalid or unreachable number

Numbers that are disconnected, ported, or roaming out of coverage fail at the network level. An HLR lookup before sending flags these so they don't count against your delivery rate or your bill.

§03

Grey-route filtering

If your traffic is routed over a grey path, operator SMS firewalls silently discard it and you may see no receipt at all. Moving to a direct operator route restores delivery.

§04

Encoding or content

A Unicode body submitted as GSM-7 (or the reverse) can be rejected or arrive garbled, and spam-like content or forbidden keywords are filtered. Read the DLR — 'rejected' versus 'expired' versus 'undelivered' points straight at the cause.

BNWritten by the BroadNet engineering team·Operating carrier-grade messaging since 2003, headquartered in Dubai·Editorial standards

FAQ

Frequently asked questions

My API call returns success but the SMS never arrives — why?: A success on submission only means the gateway accepted the message. The handset outcome comes later in the DLR, and a submitted message can still fail at the operator for an unregistered sender ID, an invalid number, or grey-route filtering. Read the DLR, not the submit response.
Does an invalid or ported number count against my delivery rate?: Yes. Sending to disconnected, invalid, or out-of-coverage numbers produces failures that lower your delivery ratio and cost you money. Run an HLR lookup first to drop them before you send.
Why do messages deliver in one country but not another?: Delivery is operator- and market-specific. A route that's direct in one country may be grey (and firewall-filtered) in another, and some regulators require a registered sender ID per market. Confirm each destination is on a direct route with a registered ID.

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