SMS marketing is a well-loved and proved over time tool to engage with your audience. As the importance of mobile phones, and then smartphones grew, a lot of brands considered messaging a part of their marketing strategy, as there are a lot of pros of text messaging. 

But there is a catch: to let the message do its work, it should be delivered. But not every SMS finds its way to the final recipient. And to measure the success of the SMS campaign, the concept of deliverability was created. The percent of deliverability means the amount of message that reached the phones of the clients.

To get the best results possible, you need to monitor your deliverability rate. But why would a text message not be delivered? Testelium put together a practical guide on how to avoid SMS delivery failure.

What are the most common reasons SMS messages are not delivered?

It’s important to know these reasons to prevent failure, because a lot of carriers may charge you for the SMS, even if it is not delivered. 

  • Your SMS doesn’t pass spam filters. If your messages are sent from alphanumeric IDs (the IDs which consist of numbers and letters) or it looks like a spam message (has suspicious links and no ways to unsubscribe), the carrier’s filter won’t deliver it.
  • You send SMS to inactive numbers. The numbers from your base might be expired, turned off, or out of the connection zone. 
  • Your text messages go through gray routes. Some providers may use unauthorized routes, avoiding the services of the official carriers. It might work, but if a spam filter finds such messages, it will block the delivery. 

What is an SMS delivery report and how to analyze it?

The delivery report notifies you about the status of your text message. However, this statement needs clarification: it notifies if your message was successfully (or not) sent from your device, but it doesn’t show if the terminal device receives it. 

So how do SMS delivery reports work then? When you send your message, it gets to the Short Message service center, or SMSC shortly, which stores and proceeds SMS further. 

You can receive several responses: of course, a successful one, meaning that your message was sent and failed. There are multiple reasons why the delivery may be negative: your carrier hasn’t yet returned a response to a submitted message, your content was problematic (it was considered spam), or your recipient number is unreachable. 

Android vs iPhone SMS delivery report — what is the difference?

The main difference between iPhone and Android SMS delivery reports is that IOS doesn’t support this feature for usual text messages. You can’t get any kind of iPhone SMS delivery report: there are no settings for that or even a third-party solution because it’s prohibited by Apple. However, iMessage, the custom texting feature of the iCloud ecosystem, can produce delivery reports, though it might not help your marketing purposes.

On another side, Android provides delivery reports, but this feature is turned off by default. You can enable it through the settings of the messenger app you’re using. 

How to test your SMS delivery?

There are ways to check your deliverability and routes, for example, with Testelium bulk SMS tests. You can test if your message is delivered with our services and get the following results:

  • successful: your message reached the final device, congrats!
  • failed: the text message wasn’t delivered; you can also see if the message was handed over to the vendor: if it was, but it wasn’t delivered to the terminal device, it was fake;
  • undeliverable: the bind is disconnected; our support can help you to detect the problem;
  • unroutable: the number of the message went offline, however, it should be back in a few minutes.

The report also provides you with additional info like if there were any changes in SMS content or your sender ID. You can check reports through the interface or free SMS sender API

Useful tips on how to Increase SMS Deliverability rate

It may look overwhelming now and a little out of your control, but actually, you can improve your SMS delivery rate. The main idea here is to play fair and not to try to trick the system. Keep your communication ecological and remember that your priority is a good relationship between your clients and your brand. But if you want an action plan, we’ve also got some practical advice.

Avoiding adding links to domains you are not in control of 

Sending foreign links can always backfire: the domains’ may change owners, the content may be erased, and your message may lead to a catfishing site eventually. Of course, it’s a hypothetical worst-case scenario, but the thread is there. 

Don’t also send links shortened by or similar services: the carrier may mark it with a red flag, and it’s understandable: any harmful content can be covered by such a tool. But the other side of the issue is that the carrier will not deliver the SMS, but still charge you. Try to shorten the link with your own site domain.

Do not send out to all users at once

The bulk SMS delivery rate is not as good as you think. When you send hundreds of messages at the same time, the carrier detects that it’s a broadcast and blocks your SMS, and your effort was in vain. And if you overuse this approach, your number may be marked as a spam number and there is no use for it for further marketing activities.

Try to send campaigns that encourage contacts to text you back

What do you do when you receive a text from your family or friends? Of course, you text them back! And it’s a goal you need to pursue: your customers should reply to your SMS. 

The dialogue is always the medium that boosts sales: you can detect what a person really needs and why, you can get to know their doubts and work with them. The personal approach also makes you look better in the eyes of customers: they remember a positive experience and lately associate your brand with a nice conversation with a manager behind the screen.

There is also a more practical benefit of customer’s responses: they are noticed by the carrier, who now perceives you as a real, trusted number.

Send from multiple phone numbers 

As we mentioned earlier, it might be harmful to conduct a massive bulk SMS campaign at once, though are two ways how to avoid this restriction: you can stretch your SMS campaign for a few days, or you can use a few different numbers to send the messages.  

The second option comes in handy if you need to text all your customers immediately. But you also use it for A/B tests: for example, prepare two different call-to-actions, and respectively send them to different people, using two numbers.

Include opt-out instruction

Opt-out is not just a gesture of courtesy, but a mandatory condition in the US, Canada, and some European countries. Moreover, it will keep the number you use out of the spam lists and distinguish the audience which is amenable to communicate with you. 

At this point, you may think that everyone is going to unsubscribe. But don’t worry — if your messages are catchy and useful, people will keep them. Those who unsubscribe — there is a high possibility that they wouldn’t interact with your business either way. 


As you can see, there are multiple reasons why text messages are not delivered. If you haven’t known what SMS delivery is and haven’t tracked it yet, it’s time to do that and optimize the weakest parts. Take care of your message content, choose proven routes and vendors, and Testelium will gladly help you with SMS delivery testing!