Why Are There No Read Receipts in SMS and MMS?
SMS and MMS remain core communication channels for mobile users and businesses, yet they lack modern features that people expect from messaging apps. One of the most common questions is why these traditional messaging protocols do not support read receipts. Unlike platforms that run over the internet, such as WhatsApp or iMessage, SMS and MMS rely on legacy telecom standards that were created long before advanced message state tracking existed. This article explains the technical design choices, network limitations, and privacy considerations that prevent SMS and MMS from offering read receipt functionality. It also explores how this limitation affects user expectations and enterprise messaging strategies in the SaaS space.
How SMS and MMS Were Originally Designed
SMS and MMS were created during a period when mobile networks focused on delivering basic connectivity rather than interactive messaging experiences. SMS was introduced using the GSM standard, which relied on the network’s signaling channel to send short messages. These channels were designed to carry minimal data, primarily for network operations, not for detailed analytics about message states.
MMS arrived later but still relied on carrier-based infrastructure rather than internet protocols. It used a store and forward system that transferred multimedia files through carrier servers instead of the direct internet based routing used by modern messaging platforms. Because both SMS and MMS were built without the expectation of advanced message tracking, features like typing indicators or read confirmations were never integrated into their core standards.
Why Read Receipts Cannot Be Added to SMS or MMS Easily
To support read receipts, a messaging system must confirm not only delivery to the device but also confirmation that the user opened the message. This requires an active data connection between the device and a messaging server. SMS and MMS do not use servers in this way. They operate as simple packet transfers within a telecom network that has no mechanism for gathering user interaction data.
Once an SMS or MMS is delivered to a device, the carrier has no visibility into what happens next. The device does not send a signal back to the network to say the message was opened. Without that signal, read receipts are technically impossible. Adding this feature would require a complete redesign of the global SMS and MMS infrastructure, something carriers have never attempted because newer internet based messaging channels already provide these features.
Why Privacy Plays a Significant Role
SMS and MMS do not support read receipts partly because of privacy expectations that existed when these technologies were created. Early telecom standards were built with minimal user tracking. The absence of read receipts aligns with a model where carriers process only the data necessary to deliver the message and nothing more.
Modern messaging applications allow users to disable read receipts as a privacy preference. SMS and MMS do not need this option because they do not collect or send read data at all. In other words, the protocol protects user reading behavior by design, not by providing a toggle.
Additionally, telecom networks operate under strict regulations that limit the type of information they can collect about user activity. Collecting read status could raise legal and compliance concerns across different countries and carriers.
How This Impacts Modern Messaging Expectations
Users today are accustomed to instant feedback in messaging apps. Features like delivered, read, and typing indicators have reshaped expectations. When people switch back to SMS and MMS, the absence of these features can feel outdated.
For businesses, this limitation affects campaign planning and customer experience. SaaS and CPaaS platforms cannot provide read receipts for SMS or MMS because carriers do not supply the data. Delivery receipts are possible in many cases, but there is still no insight into whether the recipient actually opened the message. As a result, businesses must design communication strategies around engagement trends rather than message open confirmation.
Why Read Receipts Are Available in Some Messaging Apps but Not in SMS or MMS
Messaging apps such as WhatsApp, iMessage, and Facebook Messenger run on internet based infrastructure. They use servers that continuously manage user connections. These servers can track when a message is sent, delivered, displayed, or read. This level of detail is easy to implement because all data flows through a centralized system.
SMS and MMS do not have a central server that monitors user actions. The carrier simply hands the message off to the device. Once it arrives, the process is finished. Because of this fundamental architectural difference, SMS and MMS cannot replicate features that depend on server based tracking.
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