Messaging Services - SMTP and SMPP/SMS


When you consider notification services, text delivery protocols can complicate your decision. Here we will discuss SMTP, SMPP, and SMStexting, what each means, and how their differences affect the reliability of your service.


SMTP (Simple Mail Transfer Protocol) is the protocol that sends an email. SMTP messages deliver to cell phones in text format with headlines containing numbers and symbols. However, they are actually email messages that send to email addresses assigned to each cell phone by the carrier. SMTP messages route through the Internet and, as with email, there is no charge for delivery. SMTP protocol is sometimes called “email to SMS,” “web to phone” or “standard delivery.” Suppliers sometimes market SMTP messaging as “free text messaging.”

SMPP or True SMS

SMPP (Short Message Peer-to-Peer Protocol) sends SMS (Short Message Service) text messages. SMPP is often referred to as “true SMS” or just “SMS texts.” The SMPP protocol specifically sends text messages to cell phones: one-to-one or one-to-many. True SMS text messages route through cell phone carriers who charge fees for text messaging.

The Differences 

Reliability is a big issue with SMTP messages. Delivery speed is notoriously unpredictable. SMTP messages are subject to email filters and buffers. They are accepted and delivered at the discretion of the cell phone carriers. They are monitored to protect customers from unsolicited messages and carriers can stop delivery without notifying the sender.

Domain name changes can also prevent SMTP messages from going through. This happens when a consumer changes carriers but keeps the same phone number, or when the carriers themselves change their domain names.


With SMTP messages, there is no way to confirm that your message was received, and it does not allow two-way communication. Just send it, forget it, and hope for the best.

SMS text messaging allows for reports that confirm successful delivery, explain why a text failed, and provide documentation that messages were received. Two-way communication gives senders the ability to poll recipients and solicit responses.


Most carriers outside the U.S. do not assign email address domains to cell phones, which renders SMTP messaging impossible. SMPP connections provide a global reach to nearly every country.


The FCC, under the Controlling the Assault of Non-Solicited Pornography and Marketing (CAN-SPAM) (2003) Act, regulates SMTP messages. The act prohibits senders from sending commercial email messages without recipients’ prior authorization. With headlines that contain numbers and symbols, SMTP messages often look like spam. So, permission does not guarantee that recipients will think your messages are not spam and delete them or report them as offenses. In addition, SMTP messaging falls outside the terms and conditions of most cell phone carriers.

Under the Telephone Consumer Protection Act of 1991 (TCPA), the FCC regulates SMPP. It also requires that recipients grant permission to receive automated calls and texts. Cell phone carriers and commercial interests work together to self-regulate SMPP messaging and ensure compliance to protect consumers, thereby protecting their businesses.

How Can You Tell?

Some suppliers may not be as forthcoming as others regarding what protocol they use for text messaging. So don’t hesitate to ask! Look for these sure warning signs that you may be relying on SMTP to deliver your important messages:

  • Your vendor asks for a carrier when adding a number to your contact list
  • Your contact changes carriers and no longer receives your messages
  • Your contacts experience slow delivery
  • You have a sudden increase in messages that have not been received
  • You have frequent instances of messages that are not being received

Suppliers that use SMPP want you to know they use the superior protocol for text messaging. They will be happy to tell you, and there will be no need for you to ever have to know, track or maintain information about your contacts carriers.

In Conclusion

When suppliers tout “unlimited text messaging,” dig a little deeper. Is it SMTP or SMPP? The differences are clear. There is no question that the benefits of SMPP far outweigh SMTP. So the real question here is this: Is SMTP really “free text messaging?” If cost is the only factor, why even bother sending messages that could be deleted as spam, not delivered in time... or not delivered at all?


Text messaging... it’s all in the delivery!

Puzzled by all the initials? Understanding delivery protocols are not as complicated as you may think. If you’re looking at message notification suppliers, these basics will make you a pro.

SMTP (Simple Mail Transfer Protocol) is email

  • Routed through the Internet, delivered to email addresses assigned to each cell phone by the carrier
  • No charge for delivery
  • Also called: “email to SMS,” “web to phone” or “standard delivery”
  • Delivery is at the discretion of the cell phone carriers
  • Delivery is notoriously unreliable, slow or doesn’t happen at all
  • You must collect and maintain your contacts’ carrier names

STMP messages cannot be delivered if:

  • A carrier changes their domain name
  • Your contact changes carrier but keeps the same phone number
  • Cannot confirm or document that messages were received
  • Does not allow two-way communication
  • Cannot use for international messaging

SMPP (Short Message Peer-to-Peer Protocol) Sends SMS (Short Message Service) Text Messages

  • Specifically for one-to-one or one-to-many text messaging
  • Often called “true SMS” or just “SMS texts”
  • Routed through cell phone carriers who charge fees
  • Carriers give SMS texts priority over SMTP
  • Changes in carriers or domain names do not affect delivery
  • Can confirm delivery, provides documentation
  • Two-way communications allow polling and soliciting responses
  • Allows global messaging

If you still have questions about which is best, consider this one...
If your messages are important enough to send, aren’t they important enough to be delivered?

At a Glance 



SMPP or SMS Text

Also known as:

Email to SMS, web to phone, or standard delivery

True SMS or SMS text

Specifically developed

To send email

To send text messages to cell phones

Messages routed through


Cell phone carriers

Cost per message


Assessed by cell phone carriers

Delivery reliability

Notoriously unpredictable; can be slow or not delivered at all

Notoriously fast and dependable

If consumer changes carrier but keeps the same phone number

Unable to deliver

Delivery not affected

If the carrier changes their domain name

Unable to deliver

Delivery not affected

Delivery confirmation

 Unable to confirm delivery


Documentation of receipt



Allows two-way communication





Allows recipient polling




Allows international text messaging




Complies with carriers’ terms and conditions



Federally regulated





Industry regulated



How to tell which protocol a vendor uses

•    Vendor asks for a carrier when adding a number to your contact list

•    Your contact changes carriers and is no longer receiving your messages

•    Slow delivery

•    A sudden increase in messages not received

•    Frequent instances of messages not received

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