SOFTPHONEZYou upload your list, hit send, and half your messages vanish. Bulk SMS gets filtered when it looks unsolicited to carriers, and carriers filter aggressively. The good news: deliverability is mostly about following a short list of rules. Here is why messages get blocked and exactly how to keep yours landing.
Why carriers block bulk SMS
US carriers run spam filters on application-to-person (A2P) traffic. Messages get filtered or blocked when they show the signals of unsolicited bulk sending:
- The sender is not registered for A2P 10DLC.
- There is no clear opt-in from recipients.
- No opt-out (STOP) option is offered.
- A public link shortener (like bit.ly) is used.
- The content is in a prohibited category.
- A brand-new number suddenly sends a huge burst.
The deliverability checklist
1. Register A2P 10DLC first
This is non-negotiable for US business SMS. Register your brand and campaign so carriers know who you are and what you send. See our A2P 10DLC registration guide for the full walkthrough.
2. Only message people who opted in
Send to contacts who explicitly agreed to hear from you, through a form, checkbox, or keyword. Buying lists or scraping numbers is the fastest way to get blocked and reported.
3. Make opt-out easy and honor it
Include opt-out instructions (reply STOP) and stop messaging anyone who opts out, immediately. Honoring STOP is both a legal requirement and a strong deliverability signal.
4. Identify yourself
Put your business name in the message so recipients know who is texting. Anonymous messages read as spam.
5. Drop the public link shorteners
Shared shorteners are heavily abused, so carriers filter them. If you need a link, use a branded or dedicated domain instead of a public shortener.
6. Warm up and pace your sending
Do not blast your largest campaign the moment you go live. Build volume gradually and keep a steady pace rather than sudden spikes, which look like spam.
7. Keep content clean and on-topic
Avoid prohibited categories and keep messages consistent with your registered campaign. If what you send drifts from what you registered, deliverability drops.
Do this and you will land
Registered sender, real opt-in, working opt-out, clear identity, no junk links, steady pace. That is the whole game. SoftPhonez has opt-out handling, first-name personalization, and per-recipient delivery tracking built into bulk SMS from your own Twilio number, so you can see exactly what landed and what did not.