SMS may seem simple, but it remains one of the best ways to reach your customers. It’s direct, personal, and almost always read, usually within minutes. That’s why many businesses worldwide still rely on it to connect with customers.
But when your messages don’t get through, you may lose sales, confuse customers, and frustrate your staff. In most cases, these problems stem from just a few common causes that you can easily resolve.
This blog explains why SMS delivery fails and what you can do to keep your messages moving.
8 Common SMS Delivery Issues and Solutions
SMS delivery isn’t always plug-and-play. Behind every failed or delayed message is usually something technical or procedural that you can troubleshoot. Here are the most frequent culprits and what to do about them.
1. Invalid or inactive phone numbers
One of the most common reasons an SMS fails to deliver is that the recipient’s number is invalid or no longer active. This issue often occurs due to a lack of validation of customer data during sign-up or a lack of recent updates to the mobile user’s details.
To avoid this problem, you can run regular database cleanups and use real-time number validation tools that catch typos and inactive numbers before you send.
2. Carrier filtering or spam blocks
Mobile carriers automatically scan messages for spam-like content, like shortened URLs, suspicious sender names, or heavily promotional language.
That said, keep your content clear and concise to avoid spam triggers. Then, register your sender ID with local carriers so your customers know they’re receiving information directly from you.
Ideally, you work with a reputable provider, such as Semaphore. With a reliable SMS API and support for sender ID registration, we help your messages reach more people without the technical hassle.
3. Incorrect message formatting
If you forget to use E.164 number formatting (e.g., +639999123456), include a broken link, or insert unsupported characters, your message may never reach the recipient. Philippine carriers also have strict rules: no shortened URLs and no special characters that require Unicode encoding.
Use standard GSM (Global System for Mobile Communications) characters, adhere to the 160-character limit, and test your messages across devices. Plus, always send from a pre-registered sender name and avoid vague IDs like “SMS” or “TEST.”
A clean, correctly formatted message enhances SMS delivery and ensures compliance with regulations.
4. Poor network coverage
Even if everything is correct on your end, a poor signal on the recipient’s side can delay or block delivery. Phones that are turned off, roaming, or in low-coverage areas may not receive your message immediately.
The fix here is to configure retry logic or message expiration settings in your SMS platform so messages automatically resend when the device becomes reachable.
5. Outdated or misconfigured SMS gateway
If you’re using your SMS gateway or working with a low-tier provider, you may encounter issues with routing, encoding, or compatibility. Misconfigured gateways can silently block messages or cause failed handshakes with carriers, resulting in communication issues.
Partnering with a provider like Semaphore significantly reduces this risk. Our optimized infrastructure enables you to achieve speed, compliance, and high-volume delivery. This way, you can focus on your SMS marketing strategy while we handle the technical aspects of delivery.
6. Message length or character issues
If you exceed the 160-character limit, your SMS may be split into multiple messages or corrupted during transmission. Special characters and emojis can also switch the encoding from GSM to Unicode, reducing the maximum character count to 70 per message.
Use URL shorteners when necessary, limit emojis, and verify encoding in your SMS dashboard to ensure the SMS delivery is clean and error-free.
7. Lack of user opt-in or permissions
Sending texts to people without their permission creates legal risks and increases the chance of customers blocking or reporting your number. Some carriers filter traffic that they suspect comes from purchased or scraped lists.
To stay compliant and maintain good standing, build clear opt-in flows and honor opt-outs immediately. Use simple language, such as “Text YES to subscribe,” and always confirm when someone joins.
Make opting out just as easy. Include direct instructions, such as “Text STOP to unsubscribe,” and send a quick confirmation when someone opts out.
You can also offer alternatives, such as reducing message frequency instead of completely removing a subscriber. That way, you respect their preferences while keeping the door open for future engagement.
8. High-volume throttling or rate limits
Sending bulk messages haphazardly can trigger carrier limits or slow down the delivery process. If you repeatedly send hundreds of messages without receiving enough replies, carriers may flag your traffic as spam.
You may also encounter network overload during peak times, such as holidays or significant events. Your customers may not receive your messages on time or at all.
To avoid these issues, pace your sends. For large campaigns, consider spreading out your SMS or using multiple sender IDs to ensure a smooth process.
Get Your SMS Strategy Back on Track
Most SMS delivery problems aren’t mysterious—they are simply overlooked. The more you understand the rules behind delivery, formatting, and compliance, the better your results will be.
If you want an easier way to handle it all, consider Semaphore, a provider of trusted SMS marketing for businesses.
Our SMS API, bulk messaging tools, and real-time delivery tracking allow you to send thousands of promo alerts or customer updates. We’re here to help you succeed in the world of SMS marketing.
Explore our SMS solutions today and take control of your communication.
