CLI

CLI for AI agents

Use MailBlastr from AI agent workflows and CI/CD pipelines — non-interactive sends, stdin piping, batch, idempotent retries, scheduling, and webhook feedback loops, all over plain HTTP.

MailBlastr is well suited to AI agent workflows and CI/CD pipelines: it is a plain JSON REST API with no interactive login, so an agent can drive it with curl (and jq) the moment it has an mb_ key in its environment. This page covers the agent-specific patterns. See the CLI reference for the full command surface and the CLI Quickstart to send your first email.

If your agent prefers a typed client, the official mailblastr Node SDK wraps the same endpoints — see SDKs.

Non-interactive by default

There is nothing to switch on. Every MailBlastr request is a single HTTP call that returns machine-readable JSON to stdout, with no progress indicators and no prompts. Capture the HTTP status to drive exit codes so a failed call fails the agent’s step:

status=$(curl -s -o /tmp/out.json -w '%{http_code}' -X POST 'https://api.mailblastr.com/emails' \
  -H "Authorization: Bearer $MAILBLASTR_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{ "from": "Acme <onboarding@yourdomain.com>", "to": ["delivered@example.com"], "subject": "Welcome" }')

if [ "$status" -ge 400 ]; then
  jq -r '.message' /tmp/out.json >&2   # structured error: { "name", "message" }
  exit 1
fi
jq -r '.id' /tmp/out.json

Errors always come back as a structured envelope with a name and message field alongside a non-2xx status — see the error reference. An example auth failure:

{ "name": "missing_api_key", "message": "Missing API key in the authorization header." }

Piping content from stdin

Agents generate content on the fly. Build the request body with jq and pipe it straight into curl with -d @- instead of writing temp files — --rawfile/--arg keep the generated text safely JSON-escaped:

echo "Your order has shipped." | jq -Rs '{
    from: "Acme <onboarding@yourdomain.com>",
    to: ["delivered@example.com"],
    subject: "Order update",
    text: .
  }' | curl -s -X POST 'https://api.mailblastr.com/emails' \
  -H "Authorization: Bearer $MAILBLASTR_API_KEY" \
  -H 'Content-Type: application/json' \
  -d @-

The same jq -n --rawfile html ./body.html pattern injects an HTML body from a file — see the CLI reference.

Batch sending

Send up to 100 emails in a single request by POSTing a JSON array to POST /emails/batch. Read the array straight from a file the agent wrote with -d @-:

cat emails.json | curl -s -X POST 'https://api.mailblastr.com/emails/batch' \
  -H "Authorization: Bearer $MAILBLASTR_API_KEY" \
  -H 'Content-Type: application/json' \
  -d @- \
  | jq '.data'

Safe retries

Add an Idempotency-Key header to prevent duplicates when an agent retries a failed request. Reusing the same key returns the original result instead of sending twice. The header works on both /emails and /emails/batch.

curl -X POST 'https://api.mailblastr.com/emails' \
  -H "Authorization: Bearer $MAILBLASTR_API_KEY" \
  -H 'Content-Type: application/json' \
  -H 'Idempotency-Key: welcome-user-123' \
  -d '{ "from": "Acme <onboarding@yourdomain.com>", "to": ["delivered@example.com"], "subject": "Welcome", "text": "Hello!" }'

Scheduling

The scheduled_at field accepts an ISO 8601 timestamp or natural language like "tomorrow at 9am ET" — see Schedule emails.

curl -X POST 'https://api.mailblastr.com/emails' \
  -H "Authorization: Bearer $MAILBLASTR_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
    "from": "Acme <onboarding@yourdomain.com>",
    "to": ["delivered@example.com"],
    "subject": "Your trial ends soon",
    "text": "Your free trial expires in 3 days.",
    "scheduled_at": "tomorrow at 9am ET"
  }'

Cancel or reschedule a queued email with POST /emails/:id/cancel and PATCH /emails/:id:

# Reschedule
curl -X PATCH 'https://api.mailblastr.com/emails/em_123' \
  -H "Authorization: Bearer $MAILBLASTR_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{ "scheduled_at": "in 2 hours" }'

# Cancel
curl -X POST 'https://api.mailblastr.com/emails/em_123/cancel' \
  -H "Authorization: Bearer $MAILBLASTR_API_KEY"

Closing the loop with webhooks

When an agent sends an email, it usually needs to know what happened next — delivered, bounced, opened, or replied to. Register a webhook pointing at a public URL (use a tunnel such as Tailscale Funnel, ngrok, or localtunnel during development) so MailBlastr streams signed events to your handler as they occur.

curl -X POST 'https://api.mailblastr.com/webhooks' \
  -H "Authorization: Bearer $MAILBLASTR_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
    "endpoint_url": "https://hostname.tailnet-name.ts.net/api/webhook",
    "events": ["email.delivered", "email.bounced", "email.received"]
  }'

Always verify the webhook signature before trusting a payload — the signing secret is returned when you create the webhook. See Verify webhooks.