Alphanumeric Sender ID

Alphanumeric Sender IDs allow you to send SMS messages using a custom text identifier (like your brand name) instead of a phone number. This makes messages instantly recognizable to recipients—they see “TELNYX” instead of a random number.

Alphanumeric Sender IDs are one-way only. Recipients cannot reply to messages sent from alphanumeric senders.

Format requirements

Your alphanumeric sender ID must follow these rules:

Requirement	Value
Length	1–11 characters
Allowed characters	Letters (A-Z, a-z), numbers (0-9), spaces
Must contain	At least one letter

Country restrictions: Alphanumeric senders cannot send to the United States, Canada, or Puerto Rico. Use a long code or toll-free number for these destinations.

Before you begin

To use alphanumeric sender IDs, you need:

A Telnyx account with Level 2 verification
A Messaging Profile configured with your alphanumeric sender ID
An API key

Some countries require sender ID pre-registration. Check with Telnyx support for destination-specific requirements.

Send a message

Use the send message endpoint with your alphanumeric sender ID in the from field.

curl -X POST https://api.telnyx.com/v2/messages \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "from": "YourBrand",
    "to": "+447700900123",
    "text": "Your order has shipped!",
    "messaging_profile_id": "YOUR_MESSAGING_PROFILE_ID"
  }'

import telnyx

telnyx.api_key = "YOUR_API_KEY"

telnyx.Message.create(
    from_="YourBrand",
    to="+447700900123",
    text="Your order has shipped!",
    messaging_profile_id="YOUR_MESSAGING_PROFILE_ID"
)

import Telnyx from 'telnyx';

const telnyx = new Telnyx('YOUR_API_KEY');

const message = await telnyx.messages.create({
  from: 'YourBrand',
  to: '+447700900123',
  text: 'Your order has shipped!',
  messaging_profile_id: 'YOUR_MESSAGING_PROFILE_ID'
});

console.log(message.data);

require 'telnyx'

Telnyx.api_key = 'YOUR_API_KEY'

Telnyx::Message.create(
  from: 'YourBrand',
  to: '+447700900123',
  text: 'Your order has shipped!',
  messaging_profile_id: 'YOUR_MESSAGING_PROFILE_ID'
)

\Telnyx\Telnyx::setApiKey('YOUR_API_KEY');

\Telnyx\Message::Create([
  'from' => 'YourBrand',
  'to' => '+447700900123',
  'text' => 'Your order has shipped!',
  'messaging_profile_id' => 'YOUR_MESSAGING_PROFILE_ID'
]);

import com.telnyx.sdk.ApiClient;
import com.telnyx.sdk.Configuration;
import com.telnyx.sdk.auth.HttpBearerAuth;
import com.telnyx.sdk.model.CreateMessageRequest;
import com.telnyx.sdk.api.MessagesApi;

public class SendAlphanumeric {
    public static void main(String[] args) {
        ApiClient client = Configuration.getDefaultApiClient();
        client.setBasePath("https://api.telnyx.com/v2");

        HttpBearerAuth auth = (HttpBearerAuth) client.getAuthentication("bearerAuth");
        auth.setBearerToken("YOUR_API_KEY");

        MessagesApi api = new MessagesApi(client);
        CreateMessageRequest request = new CreateMessageRequest()
            .from("YourBrand")
            .to("+447700900123")
            .text("Your order has shipped!");

        api.createMessage(request);
    }
}

using Telnyx;

TelnyxConfiguration.SetApiKey("YOUR_API_KEY");

var service = new MessagingSenderIdService();
var response = await service.CreateAsync(new NewMessagingSenderId
{
    From = "YourBrand",
    To = "+447700900123",
    Text = "Your order has shipped!"
});

Replace:

YOUR_API_KEY with your API key
YourBrand with your alphanumeric sender ID (1–11 characters)
YOUR_MESSAGING_PROFILE_ID with your messaging profile ID

US and Canada fallback

If you need to reach US or Canadian recipients, configure a fallback long code on your messaging profile. Telnyx will automatically use this number instead of the alphanumeric sender for restricted destinations. Configure this in the Messaging Portal or via the Messaging Profiles API.

Limitations

Feature	Supported
SMS	Yes
MMS	No
Inbound messages	No
US/CA/PR destinations	No (use fallback)

Rate limits

Account level	Rate limit
Level 1 (unverified)	6 messages/minute
Level 2 (verified)	60 messages/minute

Need higher throughput? Contact sales@telnyx.com.

Failover behavior

Telnyx attempts to deliver your message whenever possible. If alphanumeric delivery fails for a destination:

If a US fallback long code is configured, Telnyx uses that number
Otherwise, Telnyx may use a generic alphanumeric sender ID to complete delivery

Common errors

Error	Cause	Solution
`InvalidFromAddress`	Invalid sender format	Use 1–11 characters with at least one letter
`AlphaSenderNotConfigured`	No alphanumeric sender on profile	Configure sender ID on your messaging profile
`UnsupportedDestination`	Sending to US/CA/PR	Use a long code or configure a fallback number

Next steps

Messaging Profiles API

Create and configure messaging profiles via API

Send Your First Message

Complete messaging quickstart guide

Sender Types

Compare alphanumeric, long code, toll-free, and short codes

API Reference

Full send message API documentation

Sending Messages

Messaging Profiles

Short Code

Hosted Numbers

Opt Outs

Phone Numbers

Toll Free Verification

10 DLC

For AI Agents

Alphanumeric Sender ID

Format requirements

Before you begin

Send a message

US and Canada fallback

Limitations

Rate limits

Failover behavior

Common errors

Next steps

Messaging Profiles API

Send Your First Message

Sender Types

API Reference

​Format requirements

​Before you begin

​Send a message

​US and Canada fallback

​Limitations

​Rate limits

​Failover behavior

​Common errors

​Next steps

Messaging Profiles API

Send Your First Message

Sender Types

API Reference

Format requirements

Before you begin

Send a message

US and Canada fallback

Limitations

Rate limits

Failover behavior

Common errors

Next steps