Email broadcasts
Send newsletters and marketing campaigns to your audiences from the dashboard or the API. Schedule, segment, A/B test, and track performance.
Send to audiences or segments
Broadcast to a full audience or a narrow segment. Personalise every message with template variables, conditional blocks, and per-contact custom fields.
Campaign analytics
Open rate, click rate, bounce rate, and unsubscribe rate for every broadcast, with per-link click maps and A/B variant comparison.
Scheduling and previews
Schedule sends in any timezone, preview every template variable permutation before launch, and cancel a scheduled broadcast up to the moment it starts.
Send a broadcast
await poststack.broadcasts.send({
name: 'March Newsletter',
from: 'news@yourdomain.com',
subject: 'What\'s new in March',
templateId: 'tmpl_newsletter',
audienceId: 'aud_all_subscribers',
scheduledAt: '2026-03-28T09:00:00Z',
});Use cases
Monthly newsletters
Author a newsletter once, schedule it for the optimum send time per recipient timezone, and watch open and click metrics roll up live in the dashboard.
Product launches and release notes
Segment your audience by plan or last-active date so the launch announcement only reaches customers who will actually care. Use A/B subject lines to find the headline that converts.
Re-engagement campaigns
Build a segment for users who have not opened email in 60 days, send a focused re-engagement broadcast, and automatically unsubscribe non-responders to protect deliverability.
Event invitations and reminders
Schedule the invitation, a 24-hour reminder, and a 1-hour reminder as three sequential broadcasts pointing at the same audience. Combine with workflows for full event automation.
How it works
Broadcasts are large fan-out sends targeted at a contact audience or segment. Compose using a published template or write the HTML inline. Variables are resolved per-recipient from contact properties, so the same broadcast personalises every message. Schedule any broadcast for a future timestamp, in any timezone, and PostStack will pace the actual SMTP dispatch — typically 1,000 to 10,000 messages per minute depending on your plan — to protect deliverability. A/B testing is built in: create up to four subject-line or body variants, set a split percentage and a winner-pick window, and PostStack automatically promotes the winning variant to the remainder of the audience after the window. The broadcast list itself is filterable by status (draft, scheduled, sending, sent, cancelled) and date range, so you can find any past send in seconds. Engagement metrics — sent, delivered, opened, clicked, bounced, unsubscribed, complained — update in real time as events flow in from receiving MTAs. Per-link click maps show exactly which content drove engagement. Cancel a scheduled broadcast up until the moment it starts sending; mid-flight cancellation pauses dispatch but cannot un-send messages already delivered.
Frequently asked questions
How do broadcasts differ from transactional sends?
Transactional sends are triggered by user actions, single-recipient, and sent immediately. Broadcasts are scheduled, target an audience or segment, support A/B testing, and report engagement metrics aggregated at the campaign level.
Do you support A/B testing?
Yes — up to four variants per broadcast. Configure split percentage, choose the winning metric (open rate or click rate), and PostStack promotes the winner automatically after your chosen evaluation window.
Can I cancel a scheduled broadcast?
Yes. As long as the broadcast has not started sending, cancellation is instant. After dispatch begins, cancellation pauses further sends but cannot retract messages already delivered.
What happens to unsubscribes?
Unsubscribes are added to the suppression list immediately and prevent further sends to that address. The footer of every broadcast includes a one-click unsubscribe link, and RFC 8058 one-click unsubscribe headers are added for Gmail and Yahoo compliance.
What if a contact is in multiple audiences?
PostStack dedupes by email at send time, so the same contact never receives the same broadcast twice — even if they belong to overlapping audiences.