How to migrate from GatewayAPI to Telnyx

GatewayAPI is a Danish SMS gateway and messaging platform offering SMS, RCS and email APIs with EU data hosting, while Telnyx is a licensed telecom carrier running a CPaaS platform over its own private global IP network. On the messaging.dev Score, GatewayAPI rates 54/100 and Telnyx 78/100. This guide covers what changes at the API level when you move an integration from one to the other.

What you gain and what you lose

Channels. Both platforms send SMS, RCS and email. Moving to Telnyx adds MMS, WhatsApp and voice; you lose no channels in the move. Neither offers Viber, Telegram, Facebook Messenger or Apple Messages for Business.

Compliance. Both are GDPR-aligned. Telnyx additionally holds ISO 27001, SOC 2 and HIPAA, which matters if you handle regulated data.

Data residency. GatewayAPI hosts in the EU only (with a residency choice, no US option). Telnyx offers EU and US servers plus Asia-Pacific and South America, also with a residency choice, so you keep EU hosting either way.

Tooling. GatewayAPI ships no official SDKs, so you integrate over raw REST (or SMPP / Email-to-SMS). Telnyx provides SDKs for Node.js, Python, Ruby, Go, Java, .NET and PHP, and its docs rate “high” versus GatewayAPI’s “med”. Neither provider offers a sandbox, so you test against live credentials on both sides.

Pricing. Both are pay-as-you-go with volume discounts. GatewayAPI uses prepaid credit with no monthly fees (from €0.0061 per SMS) and grants test credits on request. Telnyx bills per message part (from $0.004 per outbound US part) and offers no free developer credit.

How the request format differs

GatewayAPI:

curl https://gatewayapi.com/rest/mtsms \
  -H "Authorization: Token YOUR_API_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"sender": "ExampleSMS", "message": "Hello World", "recipients": [{"msisdn": 4512345678}]}'

Telnyx:

curl -X POST https://api.telnyx.com/v2/messages \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "from": "+15551234567",
    "to": "+15559876543",
    "text": "Hello, world!"
  }'

Three things change:

• Endpoint. Swap https://gatewayapi.com/rest/mtsms (or gatewayapi.eu for EU-hosted accounts) for https://api.telnyx.com/v2/messages.
• Authentication. GatewayAPI sends an Authorization: Token header; Telnyx uses Authorization: Bearer with an API key. Update the scheme, not just the token value.
• Payload. sender becomes from and message becomes text. GatewayAPI’s sender is typically an alphanumeric sender ID, whereas Telnyx’s from is an E.164 number. Recipients change most: GatewayAPI takes a recipients array of objects with an integer msisdn ([{"msisdn": 4512345678}]), while Telnyx takes a single to string in E.164 format ("+15559876543"). If you batch recipients today, you will loop or fan out per recipient on Telnyx.

Migration checklist

1. Create a Telnyx account (self-onboarding) and generate an API key in the dashboard.
2. Provision a sender — an E.164 number or messaging profile — since Telnyx’s from is a number, not the alphanumeric ID you may use on GatewayAPI.
3. Map the request fields: endpoint, Token → Bearer auth, sender → from, message → text, and recipients[].msisdn → to.
4. Re-point your sending code at https://api.telnyx.com/v2/messages, optionally adopting one of the official SDKs.
5. Re-test. Telnyx has no sandbox, so validate with live credentials against a low-value test number.
6. Update your webhooks and delivery callbacks to consume Telnyx’s delivery-report format instead of GatewayAPI’s.
7. Run both providers in parallel, comparing delivery and cost.
8. Cut over once delivery rates hold, then decommission the GatewayAPI path.

Watch out for

• No free credit. Telnyx offers no free developer credit, unlike GatewayAPI’s test credits on request, so expect to fund the account to test.
• No sandbox. Neither provider has one, so there is no isolated test environment on either side.
• Per-part billing. Telnyx charges per message part, so long or multipart messages cost more than a flat per-message estimate.
• Fewer countries listed. Telnyx lists 130 countries covered versus GatewayAPI’s 200 — verify your destinations before cutover.
• Sender format. Alphanumeric sender IDs must become E.164 numbers or messaging profiles.

For a full walkthrough of the target API, see how to start with Telnyx, or view the GatewayAPI vs Telnyx comparison.