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Understanding SMS & MMS Limitations

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Why texting from desktop apps isn’t the same as iMessage or WhatsApp or RCS

SMS and MMS are powerful tools for business communication, but they come with important limitations that surprise many people, especially if you’re used to modern chat apps like iMessage, WhatsApp, Signal, or Messenger.

This guide explains why SMS/MMS behave the way they do, why they feel “old-school”, and what you can realistically expect when sending messages from a desktop program or business texting platform.

SMS is a very Old Technology

SMS was created in the early 1990s as a way to send tiny status messages over a cell network.

It was never designed for long conversations, emojis, photos, files, or group chats.

Modern apps like iMessage ride over the internet. SMS rides over old cellular control channels.

As a result, SMS has hard, non-negotiable limits built into the global telecom system, not into your software.

SMS has Character Limits

Each SMS can only carry a small amount of text:

  • Up to 160 basic characters (A–Z, numbers, and standard punctuation)
  • Up to 70 characters if you use emojis, accented letters, or special symbols

Why the difference?

Because emojis and many symbols require a different encoding, which takes up more space.

What this means for you:

  • A single emoji can cut your message limit in half.
  • Long messages are automatically split into multiple parts.
  • You’re charged per segment, not per bubble you see in the app.

Long Texts are Split into Multiple Segments

If your message goes past the limit, it gets broken into small chunks for delivery.

Typical usable space per segment:

  • 153 characters per part for standard text
  • 67 characters per part for messages containing emoji or special symbols

Even though your phone or desktop program displays everything as one bubble, the network is actually delivering multiple mini-messages.

Some older devices may show them out of order or separately.

Special Characters reduce your Limit

The following characters force SMS into a “reduced” mode with fewer characters per message:

  • Emojis 😄💀🔥
  • Accents (é, ñ, ü)
  • Fancy quotes “ ”
  • Symbols like ✓ • — €
  • Certain punctuation like { } [ ] ^ ~

This is why a message that looks short may still be split into several parts.

MMS has Strict Media Size Limits

MMS is the system used for sending photos, videos, and attachments.

It’s slightly newer than SMS, but still very limited.

Most carriers only support:

  • Images around 300 KB – 1 MB
  • Very short, low-resolution videos
  • Limited file types

Carriers often compress or shrink your media automatically.

This is why pictures sent via MMS often look blurry or low-quality.

Different carriers (Bell, Telus, Rogers, AT&T, Verizon, etc.) apply different limits, and some will even reject images that are “too big.”

Carriers change your Media

When you send an MMS:

  • Images may be scaled down
  • Videos may be re-encoded to a lower quality
  • Unsupported file types may fail silently
  • Some carriers convert large MMS messages into links instead

This isn’t something you can control.

SMS/MMS Delivery Isn’t Instant

SMS and MMS are delivered over signaling channels that weren’t designed for today’s messaging volume.

Delays can happen because of:

  • network congestion
  • cross-carrier routing
  • message length
  • media transcoding
  • spam filtering
  • device compatibility

A delay of 5–30 seconds is completely normal.

During peak times or carrier outages, it may be longer.

SMS is not iMessage/RCS

Modern chat apps have features like:

  • typing indicators
  • reactions
  • read receipts
  • high-quality media
  • fast delivery
  • unlimited length

SMS/MMS do not support these features.

Your desktop texting app must follow the same limitations your phone does when the bubble turns green instead of blue.

These limits are controlled by carrier networks, not by the software you’re using.

Why Messages may look Different

Even if you send messages from a modern desktop interface, once they reach the carrier network, they’re forced into the old SMS/MMS ruleset:

  • Long messages split
  • Emojis reduce character count
  • Media is resized
  • Special characters behave inconsistently
  • Group messages may not behave the way you expect

Your software can enhance the experience, but it cannot bypass how the global SMS/MMS system works.

Concatenation

Concatenation is the process some carriers and devices use to join multiple SMS segments into one long message. When every part of the delivery chain supports it, a long message that was delivered as several segments will appear as a single bubble on the recipient’s device.

SMS is still transmitted across the network in individual segments. Only certain carriers and devices know how to stitch those segments back together. Because of this, a message that looks like one bubble on your side may still arrive as several separate messages on someone else’s phone.

Some upstream carriers do support concatenation and will send us properly concatenated messages. Our platform can handle these inbound and interpret them correctly. However, concatenation can only be preserved if the downstream system also supports it.

Many downstream systems, including Zultys PBXs, communicate using SMPP. SMPP inherits the raw, segment-based limitations of SMS and does not support full concatenation. When a downstream PBX does not support concatenation, we must pass the message along as individual segments, even if it originally arrived concatenated from the carrier.

For outbound SMS, we send each segment in the correct order, but the receiving carrier and device are responsible for combining them. If either one does not support concatenation, the message will appear as separate bubbles.

This behaviour is not a software issue. It is a normal limitation of SMS and SMPP technology. Because of these limitations, even a properly concatenated message can still be split when delivered, depending on the capabilities of the upstream carrier, the downstream PBX, and the recipient’s device.

Practical Tips for Reliable Messaging

To get the best results:

For SMS

  • Keep messages short when possible
  • Limit emojis and special characters
  • Avoid giant paragraphs, break them into separate messages

For MMS

  • Use smaller, compressed images
  • Keep videos short
  • Avoid unusual file types

In General

  • Expect occasional delays
  • Remember long messages count as multiple segments
  • Be aware that media quality is controlled by the carrier

In Summary

SMS and MMS are universal and widely supported, but they’re old, limited technologies.

While modern apps make messaging feel instant and unlimited, SMS/MMS still follow rules created decades ago.

Our platform gives you a modern, easy-to-use messaging experience, but the underlying telecom system still imposes limits on message length, media size, delivery, and formatting.

Understanding these limits helps ensure your messages send reliably and look the way you expect.