Use this quickstart to authenticate, send transactional messages, receive deliverability events, and connect legacy SMTP flows. Samples now cover cURL, Python, Node.js, PHP, and C#.
Overview
SendInfinity’s REST API powers transactional messaging, reputation automation, and real-time analytics. Authenticate every request using your account API key, then pass JSON payloads to the endpoints below.
Base URL: https://api.sendinfinity.com
Authentication: Authorization: Bearer <API_KEY> or X-Server-API-Key: <API_KEY>
using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Text.Json;
var http = new HttpClient();
http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", "API_KEY_HERE");
var payload = new {
from = "transacional@seu-dominio.com",
to = new[] { "destinatario@example.com" },
subject = "Teste",
html = "Olá",
tracking_domain = "links.seu-dominio.com"
};
var content = new StringContent(JsonSerializer.Serialize(payload), Encoding.UTF8, "application/json");
var response = await http.PostAsync("https://api.sendinfinity.com/v1/messages", content);
Console.WriteLine((int)response.StatusCode);
Console.WriteLine(await response.Content.ReadAsStringAsync());
Webhooks
Register an HTTPS endpoint to stream delivery, engagement, and failure events. Verify every request using the X-SendInfinity-Signature header shared with Support.