Where can I download the SMS API?

SMS is not available for download. A developer/programmer is necessary to write the code that communicates with our API.

How do I know if a message was delivered to the recipient’s mobile device?

Messages sent with a long code need confirmation from the recipient. For messages sent with a short code, delivery receipts (if provided by the recipient’s carrier) can be seen on a postback URL.

What carriers do you support?

All major U.S. and Canadian carriers are supported when sending from U.S. long codes. Global long codes are available with International Extended SMS.

Is there a character limit for SMS messages?

Yes. See sending SMS messages for limits.

Can I set up an auto response?

Yes. Use a postback URL.

Are special characters or emojis supported?

Yes. All MMS messages support Unicode. When sending SMS with the SendMessage method, set the IsUnicode parameter to true.

Are picture or video messages supported?

Yes. When using the SendMessage method, specify the desired files with the Attachments parameter.

Are messages containing links supported?

Yes. The recipient can visit any URLs that are contained in your message.

Is Unicode supported?

Yes. When using the SendMessage method, set the IsUnicode parameter to true.

Can I send messages to multiple recipients?

Yes. When using the SendMessage method, the To parameter accepts multiple recipient phone numbers.

Can I send SMS messages to an email address?

The API itself does not provide a method to send SMS messages to email. However, you can create additional programming code in your system to forward any SMS messages to a desired email address.

Do international numbers support two-way messaging?

One-way or two-way messaging support is dependent upon the country of the recipient. Please contact us for further information.

Can I use my current number with your API?

To use your current number with our SMS API, you need to port the number to Esendex. Please contact us for assistance.

Do you offer vanity short codes or long codes?

Yes. Please contact us for additional information.

Do you offer toll-free SMS numbers?


What happens if someone calls the number they received an SMS from?

The caller will hear the following message: If you have received an unwanted or unsolicited message from this number please text back with the word STOP, spelled S T O P, and this provider will be blocked from sending you further messages. You will receive a final text message as a confirmation from this number to verify that you entered in STOP correctly. If you have entered STOP in error and wish to receive more messages from this provider please text back with the word RESUME. This number is currently only used for text messages. Thank you.

Can I change the message a person hears when they call my SMS long code?

You can only change the message a recipient hears when they call your SMS API long code if you use our Phone Verification API as well. You also need to have a customized incoming call script.

Will the SMS API tell me if the recipient’s number is landline or wireless?

No. However, you can use our Phone Verification API to check whether the recipient number is landline or wireless.

Do you offer after-hours support?

Yes, we offer 24/7 technical support. Note that support after business hours (9AM-6PM ET) is meant for technical emergencies only.

Are recipients required to opt in to our messaging campaign before we send them messages?

Yes. FCC/CTIA guidelines require that recipients must opt in (agree) prior to receiving notifications from your company. This is to help prevent spam and unwanted messaging.

Is there a way to prevent incoming messaging?

No. FCC/CTIA guidelines require that all recipients must have a way to opt out of messaging campaigns. Recipients have the option to send in an opt-out keyword (STOP, END, CANCEL, UNSUBSCRIBE, QUIT) at any time.

A recipient opted out. How do they begin receiving messages again?

The recipient can text RESUME to the same long code or short code that the opt-out keyword was sent to.

Is the API HIPPA-compliant?

Esendex maintains strict security policies that make our facilities HIPPA-compliant, but due to the design of SMS, SMS messages are not HIPPA-compliant.

Can you help me implement the API?

Yes. Contact our support team for help with any questions you have during your testing, implementation, and setup process.


How do I view incoming messages?

You can use the ReadIncomingMessages method of the API, use a postback URL, or if you have a live account you can view incoming (and outgoing) messages with your reports on your Esendex Client Portal.

Can I change the Sender ID the recipient sees when a message is received?

You cannot change the Sender ID or number the recipient sees when receiving a message. Recipients will receive messages from the long code(s) or short code assigned to your license key.

Why does the Esendex response show as QUEUED and not SENT after I send a message?

Immediately after submitting a request to Esendex, the initial response will show the message as QUEUED, as our system just received the request. The message will be sent out shortly or at the time you specified within your request. At that time, the response will automatically change to SENT.

Does an international recipient’s number need to be in a certain format?

Yes. To send to recipients outside of the U.S. or Canada, you need to place 011 prior to the country code within the phone number.

Is HTTPS or encryption supported with your API?


What are the IP ranges we need to allow communication to/from? – and –

How can I view the content of outgoing messages?

To view outgoing message content you need to log into your Esendex service dashboard. Expand the “Services and Usage” drop down on the left sidebar. Click “SMS API” to view the usage of that specific service. Then click on a specific license key to view data. Move to the “Details” tab to see a breakdown of daily transactions. You can then choose to view the chart to see it for a selected date range.

Is it possible to assign a unique ID to each message/batch of messages for my organization’s internal tracking purpose?

Yes. When using the SendMessage method of the API, provide a value within the ReferenceID parameter. This value will be associated with each message within your request.

Short Code

How many messages can I send per day with a short code?

There is no limit to the number of messages you can send in a day with a short code. Messages sent through dedicated short codes are sent at a rate of 300 messages per second.

Can I have multiple short codes assigned to one key?


Can I have one short code assigned to multiple keys?


Can I manage keywords if I have a short code?

Yes. With a dedicated short code, you can manage unlimited keywords.

Long Code

How many messages can I send per day with a long code?

We suggest sending up to 250 messages from one long code per day. Messages are sent at 1 message for every 2 seconds per long code.

Can I have multiple long codes assigned to one license key?


Can I have one long code assigned to multiple license keys?


Can I manage keywords if I have a long code?

You can manage your organization’s keywords through the use of a postback URL, but you cannot manage Esendex’s built-in system keywords.

Let’s start sending, together.