The short answer
Your business texts aren’t getting delivered because of A2P 10DLC, the U.S. framework that makes businesses register before they can text from a regular phone number. Unregistered messages get blocked outright, and even registered ones get filtered by carriers for spammy content, link shorteners, or missing opt-in. iMessage avoids the whole mess, because it never rides the carrier network that does the filtering.
You typed a normal message, hit send, and the app said “Delivered.” Or it said nothing, and the customer never replied. Business texting has a hidden layer most owners never see: a carrier gatekeeping system called A2P 10DLC. Here’s what it is, in plain English, and why your texts quietly disappear.
Definition
What is A2P 10DLC?
A2P 10DLC stands for “Application-to-Person messaging over 10-Digit Long Codes.” In human terms: when a business (the application) texts a person from a standard 10-digit number, U.S. carriers require that number to be registered and approved first. It’s the system carriers built to fight the flood of spam texts, and it treats your legitimate follow-up with the same suspicion as a scam.
Registration comes in two steps. You register your brand (your business, with an EIN), then each campaign (your use case, sample messages, and opt-in flow). Until that’s approved, you’re not really in business as a texter.
The blocking
Why are my texts not being delivered at all?
Because since September 2023, carriers block all unregistered 10DLC traffic to U.S. numbers outright. It isn’t throttled. It’s rejected. And here’s the cruel part: you often still get billed for the attempt even though it never arrives. If you’ve been texting leads from an unregistered number, a chunk of those messages simply never existed as far as your customers know.
“Your message was flagged as spam and not delivered.” That’s the error countless business owners hit without ever knowing why.
The filtering
I’m registered. Why do texts still not land?
Registration gets you in the door. It doesn’t guarantee delivery. Carriers run a second layer of content filtering on top, and messages get caught for a few common reasons:
- Spam-trigger content. Certain words, all-caps urgency, too many links.
- Public link shorteners. Bit.ly and friends are heavily tied to spam and get blocked often.
- No provable opt-in. If the carrier can’t see that the recipient agreed to hear from you, your message looks suspect.
- Volume spikes. A sudden burst looks like a spammer warming up a number.
Twilio, one of the biggest messaging providers, notes that even a compliant sender can expect a filtering error rate in the low single digits, and that carriers sometimes report filtered messages as “delivered” anyway to throw off spammers. So the true drop rate is partly unknowable. Industry estimates put the share of A2P SMS caught by spam filtering in the low-to-mid teens by percentage. You’re paying to send messages that a black box decides whether to deliver.
See a message that actually lands
Fill out the form and watch your phone. The text arrives in about 60 seconds, as a blue-bubble iMessage that never touches the carrier filter in the first place.
The way around it
How does iMessage avoid the delivery problem?
This is the structural advantage, and it’s simple. A2P 10DLC and carrier filtering are features of the carrier SMS network. iMessage doesn’t use that network. It travels over Apple’s own encrypted internet infrastructure, device to device. There’s no 10DLC registration to pass, no campaign to vet, no carrier content filter deciding whether your message is spam, because the carrier isn’t in the path at all.
For the roughly half of U.S. leads on iPhones, that means a message that lands as a trusted blue bubble, with a read receipt to prove it. For everyone else, you still fall back to properly registered SMS, done right, with real opt-in and clean content. The full trade-off between the two channels is broken down in iMessage vs SMS for business.
What to do
What should you actually do about it?
Three things. If you’re sending business texts from an unregistered number, stop and get registered, because you’re lighting money on fire. Clean up your sending: real opt-in, no public link shorteners, human-sounding content. And put your most valuable, trust-dependent messages, the instant lead follow-up where a reply is everything, on the channel least likely to be filtered. For iPhone users, that’s iMessage. The goal isn’t to master telecom compliance. It’s to make sure the message a paying customer is waiting for actually shows up.
Frequently asked questions
Do I really need to register for A2P 10DLC?
Why do my texts say “delivered” but the customer never got them?
Does A2P 10DLC apply to iMessage?
What gets a registered business text filtered?
Sources
- Twilio, What is A2P 10DLC: help.twilio.com/articles/1260800720410
- Twilio, full blocking of unregistered U.S. A2P traffic (Sept 2023): twilio.com/en-us/changelog
- Twilio, error 30007 “Message filtered” and compliant-sender filtering rates: twilio.com/docs/api/errors/30007
- Twilio, SMS carrier filtering in the U.S. and Canada: help.twilio.com/articles/360022449893
- Apple, iMessage security overview: support.apple.com/guide/security/imessage-security-overview-secd9764312f