SMS vs. SMTP Text Messaging

If you've been looking in to text messaging for your business, chances are you've come across two acronyms--SMS and SMTP.  They refer to two very different types of messages, and today we're going to break down the important differences. First, we need to define the two acronyms.

SMTP - Simple Mail Transport Protocol. SMTP is the standard for email on the internet and it's over 25 years old! Most cell phones are able to receive text messages in this format. In essence the phone  receives an email, and in fact, a message delivered in this fashion is sent to an address like

SMS - Short Message Service. SMS is a message system designed for cellular phones. Unlike email, SMS messages are sent to phone numbers, not addresses. They are routed through a gateway, which connects directly to the carrier's network. For our discussion SMS can be seen as interchangeable with SMPP--the Short Message Peer to Peer Protocol.

If you are looking into commercial text messaging, you need to be looking at SMS. Why? There are a number of reasons, and now we are going to explore them.

  1. An SMS message is sent via a gateway directly to the cell phone carrier, while an SMTP message, like any other email, bounces from server to server (this can often happen a half-dozen times) before it arrives.
  2. SMS messages travel over a Virtual Private Network (VPN) and are thus secure, while SMTP messages travel unencrypted around the Internet.
  3. Cell phone carriers (often reluctantly) deliver SMTP messages for free, while they charge a toll for SMS messages. Because they charge this toll, carriers have a much greater incentive to make sure SMS messages are delivered in a timely fashion. Further, as these messages are routed directly through their computers, carriers can provide you with delivery information--messages which do not arrive are called bounces. With SMTP you never know if your messages arrive.
  4. Perhaps the greatest benefit of SMS messaging over SMTP messaging is its two-way nature.  This allows your subscribers to respond to messages you send them. More than just a value-adding feature, two-way capability is necessary for commercial messaging under current United States case law.

The fourth point--about the law--leads us to an important discussion. In 2003, Congress enacted the Controlling the Assault of Non-Solicited Pornography and Marketing (CAN-SPAM) Act to curb spam. As required by the Act, the Federal Communications Commission (FCC) adopted rules that prohibit sending unwanted commercial e-mail messages to wireless devices without prior permission. This ban took effect in March 2005. The FCC’s ban covered messages sent to cell phones and pagers, if the message used an Internet address that included an Internet domain name (as seen in my Cingular example above).

The FCC’s ban did not cover “short messages,” typically sent from one mobile phone to another, that do not use an Internet address (such as an SMS/SMPP message). To help enforce its ban, the FCC required wireless service providers to provide all Internet domain names used to transmit electronic messages to wireless devices. The FCC published this list on its Web site.  Senders were prohibited from sending commercial e-mail messages to any Internet domain name on this list without the recipient’s express prior authorization.

In other words, the SMTP protocol is pretty heavily regulated when it comes to sending messages to subscribers who did not give their “express prior authorization.” However, the CAN-SPAM Act provided no regulation when it came to the SMPP protocol. Still, that doesn’t mean that you are free and clear with SMPP, thanks in large part to a widely interpreted provision of the  Television Consumer Protection Act of 1991.

One of the articles of The Telephone Consumer Protection Act of 1991 (TCPA), includes sending text messages to cell phones using an automatic telephone dialing system. The TCPA prohibits the sending of such messages “to any telephone number assigned to a paging service, cellular telephone service, specialized mobile radio service, or other radio common carrier service, or any service for which the called party is charged” 47 U.S.C. §227 (b)(1)(A)(iii).

This prohibition encompasses both voice calls and text calls, including SMS messages sent to wireless phone numbers. While it might be argued that that the SMPP protocol is not an automatic telephone dialing system, this is still a legal gray area. Moreover, the underlying directive of the TCPA can be easily extended to include the SMPP protocol, which didn’t exist when the law was initially instated. The intent of the TCPA was to make sure that consumers expressly consent to automated calls or messages sent to wireless devices given that consumers may be charged to receive such calls or messages. Since the act covers such a wide range of devices (at the time, wireless messages were meant for pagers), it is definitely possible that newer wireless technology also falls under these general guidelines. The key  again is the notion of “express written consent”, which, in the case of text messaging, means some sort of opt-in proof.

With SMS/SMPP customers can reply to messages, which is essential to the Double Opt-In process. With Club Texting's Service, new subscribers to your list receive a confirmation text message. By replying to this message, they have Double Opted In, which is commonly accepted in the industry as proof of written consent. This Double Opt In process simply does not exist in an SMTP scenario.

When you put it all together, you can see that SMS offers you more reliable delivery, secure messaging, carrier support, extended information, and most importantly, legal protection. While there are still businesses that offer SMTP messaging, flouting the law, the pennies you might save are hardly worthwhile.

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