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SMS Messages Not Delivered Or Delayed: Causes and Solutions

September 6, 2023
SMS Messages Not Delivered Or Delayed: Causes and Solutions

Are you wondering why your text messages are delayed or not delivered at all? Text messaging has become an essential communication tool in the digital age, used for personal chats as well as business dealings.

However, despite its widespread use, there are times when messages fail to deliver or are significantly delayed – which can be especially frustrating when time–sensitive information is involved.

To make sure your messages reach their destination without delay or hassle, it's vital to recognize the reasons behind SMS message delivery problems and learn how to resolve these issues. 

The following article will delve into these causes and provide helpful solutions.

What are the Reasons for SMS messages Not Being Delivered or Delayed?

In this day and age, SMS serves as a crucial aspect of our routine interactions by helping us communicate with others while also receiving vital updates from organizations. 

Nonetheless, there are times when messages simply aren't able to be sent or are delayed in their delivery - something that could easily inconvenience anyone. 

Addressing these concerns starts with recognizing what commonly leads to such occurrences and then taking action to correct them.

There could be several reasons why an SMS may not be sent. Network issues are one of the most common reasons why SMS may not be sent. If the network is down or experiencing problems, it may not be possible to send SMS.

Another reason why SMS may not be sent is an incorrect number. If the number you are trying to send the SMS to is incorrect, the message will not be delivered. This can happen if you mistype the number or if the number is no longer in use.

If you have a prepaid mobile phone, you may not be able to send SMS if you have insufficient balance in your account. Sometimes, the issue may be with your service provider. They may be experiencing technical problems that prevent SMS from being sent.

If you are experiencing issues with sending SMS, you should try troubleshooting by checking for the exact reason why your SMS is not being sent properly. 

Top Reasons for SMS Not Delivered or Delayed

The most common reasons for your SMS messages not being sent are discussed below along with possible solutions. By making the correct diagnosis, you can try to solve the problem yourself or get your service provider’s help.

Network Congestion

At peak times, the network can become congested, resulting in delays in message delivery due to an increased volume of users accessing the system simultaneously.

Solution: To avoid the text not being delivered, you can try sending messages at a different time hoping that the network is less busy. 

Insufficient Balance

If you have an insufficient balance or if the subscription is expired, your message may not be delivered.

Solution: To avoid this issue, make sure you have enough money to cover the cost of sending a message.

Roaming Restrictions

If you are traveling and your network does not provide roaming services, the message will not be received. 

Additionally, sending SMS messages to a number outside the home country can lead to delivery problems with increased expenses if international messages are not included in your data plan.

Delivery to roaming numbers is not always guaranteed, so it's important to remember to use the correct country code before the phone number and confirm that your carrier allows international SMS messaging.

Failure to collect the correct country codes may result in messages not being sent.

Solution: Before sending a message, make sure the network supports roaming services.

Message Center Number

The failure of a text message delivery can be due to an incorrectly entered Message Center Number (MCN). MCNs serve as gateways allowing SMS messages to be sent and received with ease. By sending text messages through an MCN first, these become forwarded directly to the intended recipient's phone number. 

Checking one's smartphone settings is crucial because entering the right MCN, which is provided by mobile network operators in messaging settings, helps avoid issues. It is usually provided by the network operator and can be found in the phone's messaging settings.

Solution: Double–check the message center number.

Blocked Sender

No messages will be received if the recipient has blocked the sender's number.

Solution: To resolve this, either remove the block or use a different number to send the message.

Phone Memory

If the phone's memory is overloaded, messages won't be sent.

Solution: Delete unnecessary messages or free up space on the phone.

Message Size Limit

Many networks impose a limit on the size of messages they can transmit. 

Solution: To avoid any issues, it's important to check the network's message size limit before sending the message or ensure your carrier increases the limit.

Service Outage

In the event of a network or service provider outage, messages may be delayed or not delivered at all.

Solution: To ensure your message is received promptly, it's best to wait for the outage to be resolved before sending.

SIM Card Issues

A damaged SIM card can lead to communication issues with the network, resulting in message–sending or delivery problems.

Additionally, sudden airplane mode may also indicate a bad SIM card.

Solution: If either of these occurs, users should check if the SIM card works appropriately and replace it if necessary; they may need to contact their service provider for assistance.

Incorrect Phone Number

If the phone number is incorrect, messages will fail to reach their destination.

Solution: To avoid this, double–check the phone number before sending the message.

Phone Settings

If the phone's settings are incorrect, messages may not be delivered. Several phone settings could potentially cause a message to not be delivered or delayed. 

Facing network connectivity problems is one of the most frequent issues that people encounter. However, resetting the network connection by toggling airplane mode on and off can easily resolve this problem. Additionally, outdated software may hinder message transmission or reception.

Solution: Check the phone's settings and adjust them if necessary.

Carrier Restrictions

SMS delivery is subject to carrier restrictions, which may vary by provider. Failure to adhere to these regulations can result in non–delivery of messages, fees, and even a ban on further transmissions.

Carriers have spam filters on text messaging routes and requirements for message structure; if not met, this could prevent your messages from being delivered.

Solution: To ensure the successful delivery of SMS messages, it is essential to choose the right numbers and select a vendor that can manage volume and velocity policies. 

Proven SMS templates should be used, and typical spammer behavior should be avoided to comply with carrier regulations; always check if the carrier has any restrictions before sending the message.

Spam Filters

A carrier may flag a message as spam if it contains certain characteristics usually found in spam messages. 

People call a message unsolicited if it wasn't requested. Normally, these types of messages include common spam keywords such as "click here," "free," and "money-back guarantee." 

Since they're typically sent to multiple recipients simultaneously by an unknown source, it can raise suspicions about their actual intentions. 

Suspicious messages can cause users to report them as well as unauthorized subscriptions to stop receiving future communications.

Solution: To ensure your messages are not flagged as spam, make sure you only send to recipients who have given permission.

Avoid using language or tactics associated with spam and comply with applicable laws and regulations; this includes avoiding words or phrases that may trigger spam filters.

Phone Compatibility

Compatibility issues between devices can lead to communication troubles as messages may not be received if the sender and recipient are working with incompatible devices. When the operating system or messaging application used by both parties is different, phone compatibility issues may arise. 

For instance, sending a message from an Android device to an iPhone might encounter such problems that prevent proper delivery. 

For a text message to successfully reach its intended destination, the sender's carrier network and the recipient's phone must have compatible systems. If either of these factors is compromised, delivery cannot be guaranteed. 

Additionally, poor storage or connectivity can contribute to unsuccessful sending attempts.

Solution: Before sending a message, ensure that the phones are compatible.

Restrictions on A2P SMS Messages

Some countries or carriers restrict certain senders and messaging platforms from sending messages, thereby discouraging companies from engaging in spamming or high–volume messaging.

Solution: To ensure your A2P marketing strategies remain compliant with the laws and restrictions of your country, it is essential to conduct thorough research beforehand.

However, as long as you understand the acceptable practices for sending A2P messages in your country, you can execute an effective campaign with confidence.

“Not-allowed” characters

Incompatible characters in a text can lead to difficulties when sending or receiving messages, as each operating system, messaging app, and carrier network may have its regulations concerning which characters are accepted.

This can be especially problematic for unique characters that are not supported by certain messaging apps or carrier networks, causing delivery delays or preventing the message from being delivered altogether.

Solution: To ensure successful delivery, messages must be converted or encoded into a format compatible with the receiving device or network.

It's always best to check the guidelines or rules for your messaging app or carrier network to ensure your messages are formatted correctly and contain only permitted characters.

The number is in "the Do Not Disturb list"

Phone numbers can be added to a 'Do Not Disturb' list in certain areas, provided by mobile network operators via an opt–in roster.

This blocks any messages from A2P connections for the phone owner but may cause issues if essential details such as delivery updates or order confirmations need to be received.

Solution: To avoid this issue and still prevent spam messages, some individuals only allow local phone numbers to contact them; however, this can make it difficult to reach them if you're not in the exact location.

Encourage your clients to add your A2P number to their list of permitted contacts.

What is the Difference between P2P and A2P Text Messaging?

If we talk about two individuals having a conversation through texting, that would be person-to-person texting. However, when the software or an application communicates with any specific person through texts then this process is referred to as A2P text messaging

This type of communication, A2P messaging, is commonly used to send notifications, alerts, reminders, and marketing messages to many recipients simultaneously.

In contrast, P2P messaging is more typically used for personal communication between friends, family, and colleagues. Both use the same underlying technology, but there are differences in the way they are delivered and billed.

A2P messaging is usually more expensive than P2P messaging but offers a higher level of reliability with additional features and functionalities.

The Impact of P2P and A2P Text Messaging on Deliverability

Person–to–person (P2P) texting involves sending messages from a personal phone number, with carriers limiting the number of such communications.

A2P texting, on the other hand, involves automated messages sent from a business texting service through a carrier–verified messaging platform.

This is necessary for companies to engage customers via text and ensure higher deliverability rates for various SMS campaigns such as marketing, appointment reminders, billing confirmations, and feedback collection.

Carrier–verified A2P numbers are approved by telecom carriers specifically for business messaging, allowing them to send more messages than P2P numbers without getting flagged as spam.

To use A2P messaging, the appropriate phone number is essential.

Frequently Asked Questions

  • Why are my messages not sending? 

- Several factors can lead to an SMS not being delivered. These include problems with the mobile carrier, wrong message structure, network overload or interruption, and the recipient's device being off or out of coverage area.

  • How can I ensure that my SMS messages are correctly formatted? 

- Adhering to your mobile service provider's guidelines is imperative for proper message formatting. Such rules may include a character limit, no special characters or emojis, and the correct phone number format for the recipient.

  • What is A2P messaging, and how can it help my business? 

- A2P messaging is a type of SMS used by businesses to send automated messages to customers, such as appointment reminders, shipping notifications, and promotional content. This enables companies to both increase customer engagement and streamline their communication processes.

  • Why should I consider using a reliable business texting service? 

- Rely on a business texting service to ensure your SMS messages are delivered promptly and effectively. Further, take advantage of features such as message scheduling, templates, and delivery tracking for maximum impact from your campaigns.

  • What steps can I take to improve SMS message delivery rates? 

- Collaborating with a reliable mobile service provider and following the proper format is paramount in achieving SMS message delivery success. 

- Aside from that, businesses may consider A2P messaging or business texting services, as well as keeping close tabs on their delivery rates to make needed modifications.

  • Why aren’t my texts delivered to a certain person?

- In terms of why specific individuals cannot receive your text messages, there can be several explanations behind this situation. For instance, one reason for this could be because the intended party's mobile device is either turned off or not within the range of cellular towers. 

- On another note, it might be because they have blocked you from contacting them via text on their handset as well. 

- Lastly, the message itself could contain content errors that need correcting (e.g., wrong format). To solve this dilemma, attempt texting somebody else beforehand to confirm whether sending is successful and then reach out to whichever provider appears responsible. 


Businesses that rely on timely communication might experience frustration and negative consequences when SMS messages are not delivered promptly or are delayed.

Causes of delayed or undelivered SMS messages can range from technical glitches to carrier restrictions.

To ensure intended recipients receive their messages promptly, businesses should implement proper message formatting, utilize A2P messaging services and work with reliable business texting service providers. This will help improve customer satisfaction and overall success.



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