Send email in Java via HTTP API (no SMTP)

Send email from Java with one HTTP call — no JavaMail, no SMTP. The send code with HttpClient, how to receive the reply, and error handling.

Sending email from Java usually means JavaMail and an SMTP Session to configure. A free HTTP email API replaces that with the built-in HttpClient — no transport dependency — and it can read the reply, which JavaMail’s sender can’t.

Send email in Java

java.net.http.HttpClient (JDK 11+) needs no extra library to make the call:

import java.net.URI;
import java.net.http.*;

var client = HttpClient.newHttpClient();
String base = "https://login.ollastack.com", token = "fmd_…";

// create a mailbox once
var create = HttpRequest.newBuilder(URI.create(base + "/api/mailboxes"))
    .header("Authorization", "Bearer " + token)
    .header("Content-Type", "application/json")
    .POST(HttpRequest.BodyPublishers.ofString(
        "{\"name\":\"java\",\"mode\":\"agent\",\"handle\":\"java\"}"))
    .build();
String mbx = client.send(create, HttpResponse.BodyHandlers.ofString()).body();
String id = /* parse "id" from mbx with Jackson/Gson */ extractId(mbx);

// send
var send = HttpRequest.newBuilder(URI.create(base + "/api/mailboxes/" + id + "/send"))
    .header("Authorization", "Bearer " + token)
    .header("Content-Type", "application/json")
    .POST(HttpRequest.BodyPublishers.ofString(
        "{\"to\":\"user@example.com\",\"subject\":\"Hi\",\"text\":\"Sent from Java.\"}"))
    .build();
var res = client.send(send, HttpResponse.BodyHandlers.ofString());
if (res.statusCode() >= 400) throw new RuntimeException("Send failed: " + res.body());

No SMTP Session, no Transport.send() — one HTTPS request that returns a msg_… id.

Receive the reply

A GET to the wait endpoint long-polls for the next inbound message:

var wait = HttpRequest.newBuilder(
        URI.create(base + "/api/mailboxes/" + id + "/wait?timeout=60"))
    .header("Authorization", "Bearer " + token).GET().build();
String msg = client.send(wait, HttpResponse.BodyHandlers.ofString()).body();
// parse msg.codes[0] for an OTP — extracted for you

That’s the half JavaMail’s sender can’t do — read inbound mail and pull the code without parsing MIME.

Why an API beats JavaMail / SMTP

JavaMail makes you configure an SMTP session and only sends. The built-in HttpClient call sends from an authenticated domain, returns a structured error, and also receives — useful for OTP testing or agent inboxes.

Error handling

Check res.statusCode(): on 429 back off and retry; on 4xx/5xx read the JSON error body for the code and message.

See the email API overview, the Kotlin version, and the C# / .NET version.

Get a free token — send and receive from Java, no card.

Last updated June 21, 2026. Spotted something out of date? Email hello@ollastack.com.