SMTP

Already speak SMTP? Keep your libraries. Point them at Calder and get the same pipeline — queue, retries, events, webhooks — as the REST API.

Status: specified, rolling out. The gateway spec below is final; availability follows the phases in our engineering plan. Test keys will work over SMTP from day one of the rollout.

Settings

Setting	Value
Host	smtp.calder.click
Port	587 (STARTTLS)
Username	Project SMTP username (dashboard → SMTP)
Password	Generated secret — shown once, hashed at rest

Nodemailer

mailer.js

import nodemailer from "nodemailer";

const transporter = nodemailer.createTransport({
  host: "smtp.calder.click",
  port: 587,
  secure: false, // STARTTLS — upgraded automatically
  auth: { /* user + pass from env */ },
});

await transporter.sendMail({ /* from, to, subject, html */ });

Python smtplib

send.py

import smtplib
from email.message import EmailMessage

msg = EmailMessage()
msg["From"] = "app@acme.com"
# …To, Subject, set_content…

with smtplib.SMTP("smtp.calder.click", 587) as s:
    s.starttls() # mandatory
    s.login(…)
    s.send_message(msg)

Rules of the road

TLS is mandatory — plaintext authentication is rejected, always.
The From address must belong to a verified project identity, or the message is rejected with a 550 and a dashboard explanation.
Same events, same webhooks, same usage meter as API sends — one pipeline.
Supported subset: STARTTLS, AUTH PLAIN/LOGIN, MAIL/RCPT/DATA, MIME (HTML, text, attachments), CC/BCC/Reply-To, custom headers.