A2P messaging industry is set to grow to USD 79 billion by 2030 with an average CAGR of 2.1% between 2023 and 2030. The industry is majorly bifurcated into:-

1. Promotional SMS like sales offers, discounts etc.  
2. Transactional SMS like sending OTP to a mobile number

However, there are instances where your SMS messages may not reach their intended recipients.  
In this article, we will explore the top 12 reasons why your SMS messages may not get delivered and provide insights on how to overcome these challenges.

1. Invalid Mobile Number

One of the most common reasons for non-delivery of SMS messages is an invalid mobile number. This can occur when the customer provides the wrong number or when the number is entered incorrectly into the database. It's also possible that the mobile number has been discontinued and is no longer active on the network. Additionally, attempting to send an SMS to a landline will result in non-delivery.

To ensure the accuracy and reliability of your contact list for SMS APIs, it is recommended to use a phone number validation API. This API can help identify and flag any invalid or discontinued numbers in your database.

2. Incorrect Number Formatting

Mobile numbers need to be correctly formatted for successful message delivery. When sending SMS campaigns to phones registered in different countries, it is crucial to use the correct country code and number format. This often involves dropping the leading zero from the number and adding the appropriate international dialling code.  
For example, an Indian number 9138134250 becomes 917900123456, where 91 is the international dialling code for India.

Ensuring the correct number formatting will help prevent message failures due to incorrect dialling codes or incompatible number formats.

3. Recipient's Phone is Switched Off

Although most people keep their phones connected and active throughout the day, there are instances where recipients may switch off their phones for extended periods, such as during holidays or downtime. If a phone remains switched off for a couple of days, any messages sent during that time will expire and never arrive on the recipient's device.

The recipient’s phone can also be in airplane mode.  

It's important to consider the timing of your promotional SMS messages and be aware that they may not be delivered if the recipient's phone is switched off for an extended period.

4. Roaming in a Different Country

While most mobile contracts allow services to work abroad, there are instances where certain contracts do not permit receiving texts outside of the home country. If a recipient is roaming in a different country and their contract does not support receiving texts abroad, the SMS message will not be received.

If you are aware that your recipient is traveling abroad, it's essential to confirm whether their mobile contract allows for international text message delivery.

5. Blocked or Filtered SMS

Mobile handsets often provide the option to block messages from specific numbers. If a recipient has blocked your phone number or has set up filters to divert messages from unknown senders or SMS API providers, your SMS messages will not be delivered to their inbox. This can be particularly problematic if you are using an alphanumeric sender ID or if the sender ID is set as a reply number.

Furthermore, some iPhone users have the ability to filter unknown senders into a separate list, and notification alerts may be switched off for these messages. In such cases, the SMS messages may arrive but go unnoticed by the recipient.

6. Sender ID Restrictions

Certain countries do not permit dynamic or alphanumeric sender IDs for SMS messages. If you send a text to a contact in a country with restricted sender ID regulations, your message may not be delivered. Some networks automatically switch the sender ID to a random number for delivery, while others may block the text altogether.  
For example: Singapore has some similar restrictions related to SMS and sender IDs.

It is important to stay updated on the policies regarding sender IDs in different countries and networks to ensure successful message delivery.

7. Time Restrictions on SMS Marketing

To prevent consumers from receiving marketing texts at anti-social hours, some countries impose restrictions on when marketing texts with alphanumeric sender IDs can be sent.  
For example, in France, marketing texts can only be sent between 0800 and 2000. Messages sent outside of these hours will be blocked.
India has a separate set of SMS regulations including timings and DLT registration.  

Complying with these time restrictions is crucial to ensure that your marketing texts are delivered successfully.

8. Network Filters and Anti-Spam Blockers

Networks are increasingly implementing anti-spam and phishing filters to combat rising spam problems. If your SMS message appears to be spam or could be interpreted as a phishing attempt, some networks may automatically block the text. This can occasionally result in legitimate traffic containing certain keywords being blocked as well.

To mitigate the risk of being flagged as spam, it is important to ensure that your message content does not resemble spam or contain suspicious elements. Staying informed about industry regulations and collaborating with SMS companies can help identify and block fraudulent SMS sender IDs.

9. Non-Permitted Characters

Most companies use the GSM characterset to send SMS messages. If your text contains non-standard characters outside of the GSM characterset, the network may reject your message. However, to include emoticons or special characters, messages can be sent using UTF-16 encoding. It's important to note that using UTF-16 encoding significantly reduces the number of characters per text to just 70.

To ensure successful delivery of SMS marketing messages, it is recommended to identify and avoid non-standard characters in your SMS messages. You can use a unicode character detector to identify any non-standard characters that may cause delivery issues.

10 Do Not Disturb (DND) Service

Some networks offer a "Do Not Disturb" service that allows users to opt out of receiving any marketing texts. If a subscriber activates this service, they will not receive SMS messages from marketers or businesses. It's important to respect these preferences and avoid sending SMS messages to individuals who have opted out of receiving them.

11. Restrictions from Operators

There are times when operators block some SMS routes. This can cause a delay in your SMS being delivered as these restrictions provide re-routing. These temporary delivery issues can significantly affect deliverability. Although, you can easily analyse your SMS campaign using an SMS dashboard provided by service providers like Message Central.  

12. Problems on Recipient’s End

Recipient could have opted out of your SMS campaigns or could have blocked your phone number. This is a highly likely explanation for some of the SMS messages not being delivered or read.  

In conclusion, while SMS messaging offers a convenient and efficient communication channel, there are several factors that can affect the successful delivery of your messages. By understanding these potential challenges and implementing best practices, you can improve the deliverability of your SMS campaigns and ensure effective communication with your audience.

Send SMS with Message Now

Message Now is an SMS API provider by Message Central. The platform is trusted by fastest growing businesses across countries. With the best SMS routes and competitive prices, Message Now is one of the best SMS API providers in the industry.  

You can get in touch with the team to access the SMS APIs.