Clusters

Why a send needs a named environment, and why transactional and bulk stay apart.

A cluster is a named sending environment with its own hourly and 24-hour capacity. Every send, SMTP credential, and delivery event belongs to one cluster. Customer clusters send from a shared IP.

Before you start

  • Add a payment method. Without one, Add cluster sends you to Billing first.
  • Until your team has production approval, you can have one live cluster. Creating another returns you to Clusters with an approval notice.
  • Creating and changing clusters needs the Team Administrator role.

Create a cluster

Your first cluster is made for you on Get started. Answer What type of email will you send? and What's the most you'll send in a day?, then select Start free trial. The cluster is named after your team.

To add another cluster:

  1. In the sidebar, open Sending → Clusters, then select Add cluster.
  2. Enter a name. Use lowercase letters, numbers, and hyphens, with no spaces.
  3. Under Email type, choose Transactional or Marketing.
  4. Under How many emails do you send an hour?, drag the slider or select a plan icon. PostShiba picks the smallest plan that covers it. Not sure? Start small and resize later.
  5. Select Add cluster.

The cluster starts on the shared sending pool. Its SMTP host appears once the shared IP is attached. PostShiba also issues a first SMTP credential, which you can see under Connect on the cluster page.

Transactional or marketing

The type is locked after create. Create another cluster when you need the other type.

Dashboard choice API classification Use it for Unsubscribe headers
Transactional transactional Receipts and resets Not added
Marketing bulk Campaigns and newsletters PostShiba adds one-click List-Unsubscribe

Marketing is disabled when no shared marketing IP is free. See How do recipients unsubscribe? for when the header is added.

Manage a cluster

Open a cluster from Clusters. The page shows traffic, capacity for the hour and the last 24 hours, and recent events.

Control What it does
Send test Opens the test-send form. See Send test emails.
Domains Opens your sending domains.
Sending Guide Shows SMTP, HTTP, and REST recipes and framework guides for this cluster.
Connect Lists and issues SMTP credentials.
Resize Changes the plan. Upgrades bill the rest of the period now. Downgrades credit the next invoice.
Advanced → Edit cluster Renames the cluster.
Advanced → Suspend or Resume Pauses or restarts sending on the cluster.
Advanced → Teardown Stops sending for good. The row stays for history.

When capacity boosts are enabled for your account, Boost appears next to Resize. See How do capacity boosts work?.

Create fields, hosts, and teardown over the API are on Clusters. Extra IPs are on How do dedicated IPs work?.

Next steps