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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.

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Format requirements

Your alphanumeric sender ID must follow these rules:
RequirementValue
Length1–11 characters
Allowed charactersLetters (A-Z, a-z), numbers (0-9), spaces
Must containAt 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.

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Before you begin

To use alphanumeric sender IDs, you need:
Some countries require sender ID pre-registration. Check with Telnyx support for destination-specific requirements.

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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"
  }'
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

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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.

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Limitations

FeatureSupported
SMSYes
MMSNo
Inbound messagesNo
US/CA/PR destinationsNo (use fallback)

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Rate limits

Account levelRate limit
Level 1 (unverified)6 messages/minute
Level 2 (verified)60 messages/minute
Need higher throughput? Contact sales@telnyx.com.

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Failover behavior

Telnyx attempts to deliver your message whenever possible. If alphanumeric delivery fails for a destination:
  1. If a US fallback long code is configured, Telnyx uses that number
  2. Otherwise, Telnyx may use a generic alphanumeric sender ID to complete delivery

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Common errors

ErrorCauseSolution
InvalidFromAddressInvalid sender formatUse 1–11 characters with at least one letter
AlphaSenderNotConfiguredNo alphanumeric sender on profileConfigure sender ID on your messaging profile
UnsupportedDestinationSending to US/CA/PRUse a long code or configure a fallback number

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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