Failed Delivery? Top Factors That Affect Message Delivery

Posted by Bryan Dingwall on December 1, 2016

In spite of its popularity and ease-of-use across the world, SMS delivery is not always guaranteed, and several factors influence the successful delivery of sent messages. From number validity to routing factors, this article will address some of the top factors that affect message delivery. If you’re a mobile app developer, you should take them into consideration when building and testing your apps.

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Phone number validity

Perhaps, the most common factor that impairs message delivery is an invalid or non-existing number. Sending a text message to an invalid number is like throwing a stone to the moon—it will not reach, and can come back to hit your head.

Here are some reasons that can cause a number to become invalid.

a)  Incorrect/non-existing phone number: Users can change phone numbers and carriers without updating their contacts about the changes. Also, users sometimes provide incorrect phone numbers with missing or misaligned digits. Consequently, when sending an SMS to an end user with such an invalid number, the text message fails to send.
 
b)  Recipient phone number inactive: When the supposed recipient’s phone number is switched off, or if the number is out of network coverage for an extended period of time, the message is likely to expire, and won’t get delivered. Text messages usually have a delivery validity period, and if the waiting period elapses when the phone number is still inactive, the recipient will not receive the message.
 
c)  Incorrect international country code: When sending an SMS to another country, you need use the right format with the international calling code. For example, text messages sent to the U.S. must begin with 1 because it is the international prefix for the country. Click here for a list of international calling codes. Furthermore, the number included in the international country code should be in the correct format. In some countries, particularly in Northern Europe, when sending a message from within the country without including the international code, a user must add a 0 at the start of the phone number. And, when the same number is used for international communication, the 0 should be removed.
 
d)  Sending a message to a landline: In most countries, landlines do not have in-built SMS support capabilities. So, cases of failed SMS delivery are usually experienced due to rejection of the messages.
 

Filtering content

Filtering and banning some type of messages is another critical factor that affects message delivery. Some countries have specific messaging restrictions, and without circumventing the obstacles, successfully delivering text messages isn’t possible.

For example, in China and Saudi Arabia, messages are meticulously filtered to control the information citizens receive. In Japan, it is illegal to include a URL in the body of a message, and in India, delivery of promotional messages is limited between 9 A.M. and 9 P.M. (IST).

So, before rolling out a mobile app with messaging functionalities, ensure you are conversant with country specific stipulations to ensure you attain the highest text delivery rate possible.

Besides government regulations on the messages content, another issue is what the carriers will permit. Most mobile communications companies around the world filter or ban some text messages to cushion customers from illicit content, such as phishing messages, spam messages, or other unsolicited content.

Additionally, most mobile operators also safeguard their revenue sources through thwarting Person-to-Person (P2P) messages from being delivered by means of Application-to-Person (A2P) methods. The carriers also disallow A2P messages from using P2P channels.

Carriers have employed different techniques for addressing the risks of spam and phishing. While some have relied on their respective country’s regulations to tackle these concerns, others have used technology to filter and block these unwanted messages. And, sometimes, the filters block legitimate traffic, which lead to failed SMS issues.

Here are some techniques used for filtering messages.

a)  Incorrect sender ID: Different countries and operators have different regulations on the acceptable sender IDs. Typically, most carriers around the world filter alphanumeric sender IDs. It is the easiest technique to ward off illicit content since all P2P traffic comes with a numeric sender ID. Operators also employ sender ID filtering on P2P channels to prevent the transfer of A2P traffic.
 
For example, in the U.S. and Canada, only numerical sender IDs are permitted, and every A2P messages must be sent from a text short code, whereas the U.K allows alphanumeric sender IDs.
 
So, to ensure maximum SMS delivery, users should use the right sender ID, particularly for international text messages. In addition, it’s good to randomize sender IDs because some spam filters will block repeated messages from the same sender, whether they are numeric or alphanumeric.
 
b)  Keyword filtering: Most carriers scan the sent messages content and will block any text with keywords indicating unacceptable activity. Sexual, political, or religious content may not pass through the spam filters. To avoid a situation when text message fails to send, a user should send only legitimate content and avoid words deemed to be sensitive.
 
c)  Repeated messages: Sending the same message over and over again puts you in the radar of spam filters. Therefore, frequently randomizing the content of the message can reduce chances of being caught.

 

For example:

Message 1: Your Pin Code is 3453

Message 2: To verify your account, enter 5351 in the app

 

Routing factors

Routing is also essential in determining message deliverability. In the telecommunications industry, numerous routes are employed for delivering text messages; though, routes differ in capacities and functionalities.

Whereas some channels will yield maximum deliverability with all possible filters, others will result in high latency or even non-sent messages. So, when developing a mobile app with SMS capabilities, ensure you employ the best possible routing to guarantee optimal message delivery.

Here are some ways routing affects the delivery of text messages.

a)  Using cheap routes: The telecommunications industry is littered with uncouth techniques intended to maximize gains easily. For example, tactics like SIM boxes and “grey route traffic” are unlawful methods some players employ to connect to the telecommunications network at very minimal costs.

Using such unauthorized means of sending messages impairs message delivery because mobile network operators usually shut them down. Therefore, it’s important you use trusted direct connections, and avoid cheap routes that can increase the points of failure.

b)  Portability issues: Portability allows users to change from one network to the other without changing their existing phone number. However, at times, this technology malfunctions and leads to failed SMS issues. For example, a user can port to another network and start experiencing poor connection issues. Thus, network visibility tools should be used to ensure messages are appropriately routed over the correct connection.

Other factors

Message delivery can also be affected because of several reasons, such as a recipient’s inbox becoming full, frozen messaging application, roaming limitations, and errors on operator’s SMS servers.

Some phones cannot accept some types of messages, such as WAP push messages, binary text messages, or texts with special characters.

Different operators and countries stipulate different SMS encoding standards. So, when a text message fails to send, it could mean the wrong encoding was used. For example, some carriers in Europe will not deliver messages sent in Unicode characters.

Minimize Failed Message Delivery

Since the deliverability of messages is not flawless, you should take into consideration the above factors and aptly build an app that will offer optimal SMS delivery to users. Failed delivery of SMS is distasteful, and can make users desert your app easily. Fortunately, Zang offers a robust and an efficient platform to ensure you build an app that offers minimal failed delivery of sent messages.

Topics: Phone Numbers, SMS, messaging