Which sending feature should I use?

MailBlastr has two ways to send mail, built for two different jobs. Use transactional sends (POST /emails) for messages you trigger for a single person from your application — and campaigns for one campaign sent to many contacts at once. Both send from a verified domain; they differ in how you address recipients and how unsubscribes are handled.

At a glance

Use transactional (POST /emails) when…

• The email is for one person and triggered by something they did — a signup, a purchase, a password reset request.
• You already know the recipient address at send time and want to pass it directly.
• You need a programmatic, low-latency send straight from your backend.
• Examples: order receipts, password resets, email verification, magic links, security alerts, one-off notifications.

A transactional send takes the recipients inline and returns an email id immediately:

import { MailBlastr } from 'mailblastr';

const mb = new MailBlastr('mb_xxxxxxxxx');

const { data, error } = await mb.emails.send({
  "from": "Acme <receipts@yourdomain.com>",
  "to": ["customer@example.com"],
  "subject": "Your receipt",
  "html": "<p>Thanks for your order!</p>"
});
console.log({ data, error });

Use a campaign when…

• The email goes to many people at once — everyone on a list, not one triggered recipient.
• It is marketing or newsletter content where recipients must be able to unsubscribe.
• You want MailBlastr to fan the message out across a sending domain’s contacts and track per-campaign performance.
• Examples: monthly newsletters, launch announcements, promotions, re-engagement campaigns.

A campaign targets a sending domain — its contact pool — instead of inline recipients. You create the draft, then send it — MailBlastr delivers to every subscribed contact and appends a one-click unsubscribe footer.

1. Create the campaign (draft):

import { MailBlastr } from 'mailblastr';

const mb = new MailBlastr('mb_xxxxxxxxx');

const { data, error } = await mb.campaigns.create({
  "domain": "yourdomain.com",
  "from": "Acme <news@yourdomain.com>",
  "subject": "March newsletter",
  "html": "<p>What we shipped this month…</p>"
});
console.log({ data, error });

2. Send it (optionally pass scheduled_at), using the id returned from the create call:

import { MailBlastr } from 'mailblastr';

const mb = new MailBlastr('mb_xxxxxxxxx');

const { data, error } = await mb.campaigns.send('CAMPAIGN_ID');
console.log({ data, error });

Transactional vs. marketing: the compliance line

The endpoint split mirrors a legal one. A transactional email is triggered by a user action or required for compliance — order confirmations, password resets, account notices — and recipients cannot unsubscribe from it; it’s an essential, expected message. That’s why POST /emails carries no unsubscribe footer.

A marketing email is anything that isn’t transactional: promotions, newsletters, product updates. These are regulated by laws such as CAN-SPAM (US) and CASL (Canada), and recipients must be able to unsubscribe. That’s why campaigns append a one-click unsubscribe automatically.

See the full emails API, campaigns, and audiences references.