Why your Text Messages are not Delivering: 15 Common Factors Affecting SMS Delivery Rate

Alexa Lemzy August 16, 2022
Women walking in the corridor trying to send a text message

When launching an SMS marketing campaign you start out hoping your message will get to all intended recipients. However, SMS deliverability is rarely 100% when sending a large number of texts. Given that every text sent comes with a cost, it’s recommended that you check how many messages were successfully sent and investigate the ones that were not.

Issues affecting SMS deliverability can come from the communication route, the wording of your messages or even from the receiver’s phone.

Here are the most common situations when text messages generally don’t go through and the necessary steps to avoid or fix them.

Gray Routes

All SMS routes are not created equal. As SMS grows, it has become increasingly common for application-to-person (A2P) messages to be sent via gray routes , which basically bounce around to different locations first before making their way to their final destination. Of course, on the way, the message may get lost or be deemed as spam and, in the end, never make it to its destination.

CEO of Dialogue Group, Perry Offer, has expressed concern not only about the deliverability of messages through these routes, but also that many of the senders employed fraudulent routing methods that allowed them to avoid paying. Perry affirmed that billions of dollars in revenue were being lost because of these routes.

Recently, groups such as AdaptiveMobile, a mobile security company, have developed tools to detect gray routes and intercept messages being carried on them. They can detect the origin of the messages and notify operators so that they can recover their revenue. Ideally, messages will be either sent locally or internationally through a “1-hop strategy” that connects directly to operators, ensuring deliverability.

Carrier Spam Filters

If you send a message that looks like spam, whether or not it actually is spam, chances are the carrier will filter it out and the recipient will never get it. So, how can you prevent this from happening? Here are some things that cause carrier filters to discard messages as spam:

  • Don’t use alphanumeric sender IDs. Most carriers assume these are spam. Use only numeric sender IDs instead.
  • Mass identical body messages. You may be doing a marketing campaign push and sending messages to your entire customer list. That’s fine, except that massive numbers of identical messages tend to set off spam alarms. So, break up the messages into different groups and vary the body message to avoid being marked as spam.
  • Create different sender IDs. Some carriers filter out messages from the same ID. To avoid this, create multiple numeric sender IDs and use a system where you randomly rotate them to avoid any user always getting a message from the same ID.
  • Include opt-out instructions. If customers don’t know how to opt out of your SMS programme, then you’re more likely to get marked as spam. Be sure to provide clear opt-out instructions to improve your reputation and avoid being labelled as spam.
  • Try to exclude common spam words from your message and make sure to only use certain spam-sensitive terms in their appropriate context.
Mobile Tower

Phone Issues

Sometimes you’ve done everything right – you’re sure the messages weren’t sent through gray routes and you created various numeric sender IDs – but your message still didn’t get through. This could be an issue with the customer’s phone. Any of the following issues could disrupt a message from being delivered:

  • The phone is turned off. No activity can be registered if the phone is off.
  • The phone memory card is full. If the memory card is full, no more data is able to get through.
  • The phone is roaming. The phone is out of reach of a signal and therefore can’t receive any new messages.
  • The number doesn’t exist or has been disconnected. After a period of time of being disconnected owing to lack of payment or lack of use, a phone number can be deleted from a carrier’s services. You can easily check a number’s validity using carrier lookup tools.
  • It’s a landline. Sometimes you’ve imported your SMS contact list from your email list and you end up sending SMS messages to customers’ landlines. Though some countries do support SMS messages on landlines, the majority don’t. Chances are, if you’re reaching a landline, your message will not be delivered.

Sometimes, their phone is working just fine, but you didn’t manage to enter the right number:

  • The international code hasn’t been included. If you’re sending messages internationally, you need to include an international country code in order to reach the client. People generally don’t include their international country code when filling out forms either online or in-store, and if your SMS company is in another country you’ll have to update your list to include any international codes the customers left out.
  • The international code format is wrong.This is a common mistake. Each country has its own coding system, so you may have to research the correct dialling format to reach a customer successfully.

Other times it’s a language issue:

  • A message that’s sent in a different alphabet (e.g. Arabic, Japanese, Chinese) and is destined for a carrier that supports another alphabet, or that contains accents or different characters, is often displayed incorrectly. That can cause it to be marked as spam. Some messaging services contain transliteration tools that prevent this from happening.

Phone Number Portability

It’s possible for clients to switch from one carrier to another and still maintain the same phone number. This is very convenient to the client; however, it does come with its drawbacks. If your messages were getting through just fine with one carrier, the new carrier may decide that they’re spam and stop delivering them. The client likely won’t be aware that this is happening and assume that you stopped sending them messages.

You can get around this by doing a network look-up for your client list, but it can be an expensive and laborious practice. Some carriers don’t support this, making it even more difficult. Unfortunately, chances are that if this is why your client is no longer receiving your messages, it can be difficult to recover the former level of message deliverability.

Why text message marketing is here to stay

Text messaging has been a huge boon to businesses. Prospective customers who receive text messages show a 40% higher conversion rate than those not contacted via SMS. A staggering 89% of mobile users prefer receiving texting updates from brands, which turns SMS into a primary form of customer support.

SMS marketing has generated impressive returns on investment for its users since clients now spend two times as much time sending texts as they do sending emails. Avoiding gray routes, avoiding looking like spam, and making sure you have the correct country code and language tools – all these steps will help you improve your deliverability rates significantly.

Alexa Lemzy


Customer support person. Interested in customer success, growth, marketing and technology. Passionate about content, reading and travel.

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