Transactional email that treats you like a partner.

Send receipts and password resets over REST, SMTP, or HTTP inject for one fixed monthly price. When something goes wrong, we pause one domain, not your whole account.

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Send a receipt Transactional
1curl https://app.postshiba.com/api/v1/emails \ 2 -H "Authorization: Bearer $POSTSHIBA_KEY" \ 3 -H "Content-Type: application/json" \ 4 -d '{ 5 "from": "receipts@example.com", 6 "to": ["ana@example.com"], 7 "subject": "Your receipt", 8 "html": "<p>Thanks for your order.</p>", 9 "unique_args": {"order_id": "ord_4821"} 10 }'
1swaks --server smtp.postshiba.com:587 --tls \ 2 --auth PLAIN --auth-user smtp_9 \ 3 --auth-password "$SMTP_PASSWORD" \ 4 --from receipts@example.com \ 5 --to ana@example.com \ 6 --header "Subject: Your receipt" \ 7 --header 'X-Capsule-Unique-Args: {"order_id":"ord_4821"}' \ 8 --body "Thanks for your order."
1curl https://inject.postshiba.com/api/inject/v1 \ 2 -u "smtp_9:$SMTP_PASSWORD" \ 3 -H "Content-Type: application/json" \ 4 -d '{ 5 "envelope_sender": "receipts@example.com", 6 "recipients": [{"email": "ana@example.com"}], 7 "content": { 8 "html_body": "<p>Thanks for your order.</p>", 9 "headers": {"From": "receipts@example.com", 10 "Subject": "Your receipt", 11 "X-Capsule-Unique-Args": "{\"order_id\":\"ord_4821\"}"} 12 } 13 }'
  1. Accepted 201 {"queued": true} 10:42:01
  2. Processed Queued on cluster production 10:42:01
  3. Delivered 250 2.0.0 OK 10:42:02
  4. Webhook POST hooks.example.com 200 10:42:02

Same events on every path, with order_id on each one.

Where PostShiba starts costing less.
Monthly bill by email volume: PostShiba against Postmark At 1,000,000 emails a month spread evenly, PostShiba Small costs $49 and Postmark costs $775.
1,000,000 ≈ 1,389 an hour · 33,334 a day, spread evenly
Postmark
$775
Basic 1.5M
PostShiba
$49
Small · 40,000/hr · 240,000/24h
At this volume
Save $726 a month
94% less than Postmark. PostShiba costs less at every volume shown.

Assumes sends are spread evenly across the month, the way PostShiba capacity is meant to be used. Bursty senders should size for their busiest hour. Competitor bills use USD list prices from public pricing pages, September 2026, before tax and add-ons. Postmark: Basic tier committed volume steps, plus Basic overage.

One monthly price per cluster, sized for your busiest hour. No per-email overages and no per-domain or per-tenant fees. Explore capacity pricing

Pause one domain, not your whole account.

When a problem can be contained to one sending domain, we pause that domain and work with you on recovery.

One bad domain. Two responses.

Other providers

0 of 4 sending

Everything delivering normally. A leaked API key is sending spam from billing.example.com. Account terminated. Every domain stopped, including the ones that did nothing wrong. Support ticket open. Password resets and receipts are not going out.

PostShiba

4 of 4 sending

Everything delivering normally. A leaked API key is sending spam from billing.example.com. billing.example.com paused. The other three keep delivering while we work on it with you. Key rotated. billing.example.com restored.

Pick an incident, click a domain to make it the one that goes wrong, or step through the timeline. Account-wide abuse or compromise may require a broader pause to protect your customers and the network.

Answers and guardrails, built in.

Trace every message, block bad recipients before they queue, and share the network only with reviewed senders.

See why an email did not arrive.

Every message keeps its events with the receiving server's exact response. The same events reach your webhook, signed, in the SendGrid event format.

Your receipt

To jo@example.net From receipts@example.com

  1. Processed Queued on cluster production 10:42:01
  2. Bounce 550 5.1.1 user unknown 10:42:03
  3. Suppressed Hard bounce. Future sends skip this address. 10:42:03
  4. Webhook POST hooks.example.com 200 10:42:04

Block bad recipients before they queue.

The email firewall stops temp mail, free mailboxes, plus-addresses, and listed domains before send.

Firewall
  1. jo@example.net Queued
  2. k7x2@tempmail.example Blocked
  3. mia@freemail.example Blocked
  4. sam+deals@example.org Blocked
  5. ana@blocked.example Blocked

Turn a check off to let its sends through.

We know who sends with us.

Every account needs production approval before sending to external recipients. Until then, build and test with your team.

Production approval
  1. dev@example.com Delivered
  2. ops@example.com Delivered
  3. ana@example.net Delivered
  4. jo@example.org Delivered
  5. sam@example.org Delivered

Approved for external recipients.

Send with a provider that works with you.

Sign up and start sending today. Your first cluster includes 7 days free.

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