Postmark

Best for: Prototypes and side projects - free to start, no sales call; AI agents and automation - an agent-ready surface (MCP / llms.txt); Teams needing broad API coverage out of the box

Avoid if: You have strict compliance requirements

Pricing model

Hybrid (base + usage) [2]postmarkapp.com/pricing“Free. $0.00 · Test your integration with 100 emails/month ; Basic. $15.00 · For solo developers and smaller teams ; Pro. $16.50 · For start-ups and small businesses.”postmarkapp.com/support/article/1107-how-does-monthly-pricing-work“Dedicated IPs: Starts at $50/month per IP. Our fully managed dedicated IPs are available to customers sending 300,000 emails per month or more.”buildmvpfast.com/api-costs/email“Best deliverability: Postmark ($15/mo + $1.80 per 1K extra)”

Published pricing

✓ Yes [3]postmarkapp.com/pricing“Free. $0.00 · Test your integration with 100 emails/month ; Basic. $15.00 · For solo developers and smaller teams ; Pro. $16.50 · For start-ups and small businesses.”

Free tier

✓ Yes [4]account.postmarkapp.com/sign_up“Sign up for Postmark in 30 seconds and get your first 100 emails for free.”postmarkapp.com/pricing“Free. $0.00 · Test your integration with 100 emails/month”

Free tier details

100 emails/month, never expires or runs out [5]account.postmarkapp.com/sign_up“Sign up for Postmark in 30 seconds and get your first 100 emails for free.”postmarkapp.com/pricing“Free. $0.00 · Test your integration with 100 emails/month”

Self-serve signup

✓ Yes [6]account.postmarkapp.com/sign_up“Sign up for Postmark in 30 seconds and get your first 100 emails for free.”

Requires sales call

✗ No [7]account.postmarkapp.com/sign_up“Sign up for Postmark in 30 seconds and get your first 100 emails for free.”

Enterprise plan

✓ Yes [8]postmarkapp.com/support/article/1107-how-does-monthly-pricing-work“Dedicated IPs: Starts at $50/month per IP. Our fully managed dedicated IPs are available to customers sending 300,000 emails per month or more.”

• Transactional send
• Marketing / broadcasts
• Inbound parsing
• Templates
• Batch send
• SMTP relay
• Dedicated IP
• Analytics

Supported actions

send_email, send_batch_emails, send_bulk_emails, get_bulk_email_status, get_delivery_stats, get_bounces, get_bounce, get_bounce_dump, activate_bounce, send_email_with_template, send_batch_with_template, push_templates_to_another_server, get_template, create_template, edit_template, list_templates, delete_template, validate_template, get_server, create_server, edit_server, list_servers, delete_server, list_message_streams, get_message_stream, edit_message_stream, create_message_stream, archive_message_stream, unarchive_message_stream, search_outbound_messages, get_outbound_message_details, get_outbound_message_dump, search_inbound_messages, get_inbound_message_details, bypass_rules_for_blocked_inbound_message, retry_failed_inbound_message, get_message_opens, get_opens_for_single_message, get_message_clicks, get_clicks_for_single_message, list_domains, get_domain, create_domain, edit_domain, delete_domain, verify_dkim, verify_return_path, verify_spf, rotate_dkim_keys, list_sender_signatures, get_sender_signature, create_sender_signature, edit_sender_signature, delete_sender_signature, resend_signature_confirmation, verify_spf_for_signature, request_new_dkim_for_signature, get_outbound_overview_stats, get_sent_counts, get_bounce_counts, get_spam_complaints, get_tracked_email_counts, get_email_open_counts, get_email_platform_usage, get_email_client_usage, get_click_counts, get_browser_usage, get_browser_platform_usage, get_click_location, list_inbound_rule_triggers, create_inbound_rule_trigger, delete_inbound_rule_trigger, list_webhooks, get_webhook, create_webhook, edit_webhook, delete_webhook, get_suppression_dump, create_suppression, delete_suppression, create_data_removal_request, check_data_removal_request_status [9]postmarkapp.com/developer/api/email-api“This endpoint is solely responsible for sending emails with Postmark through a specific server. Please note that the batch endpoint accepts up to 500 messages”postmarkapp.com/developer“API reference. Get straight to the details of every HTTP request available through Postmark's REST API. Overview → · Email API → · Bulk Email → · Bounce API →”postmarkapp.com/api-explorer“Use our API Explorer to send API requests directly to your Postmark server or account. Server API; Account API.”

Input types

JSON [10]postmarkapp.com/developer/user-guide/send-email-with-api“Sending single emails through Postmark is as simple as sending an HTTP POST request to our /email endpoint with the JSON message attached to the body.”

Output types

JSON [11]postmarkapp.com/developer“API reference. Get straight to the details of every HTTP request available through Postmark's REST API.”postmarkapp.com/developer/user-guide/send-email-with-api“Sending single emails through Postmark is as simple as sending an HTTP POST request to our /email endpoint with the JSON message attached to the body.”

Webhooks

✓ Yes [12]postmarkapp.com/developer/api/webhooks-api“Webhooks API lets you manage webhooks for a specific Transactional or Broadcast Message Stream.”postmarkapp.com/developer/webhooks/webhooks-overview“A webhook is the act of Postmark making an HTTP POST request to your application's API when an event occurs.”postmarkapp.com/email-webhooks“Postmark's webhooks notify your application about key message events such as bounces, deliveries, opens, clicks, and spam complaints.”

Sandbox / test mode

✓ Yes [13]postmarkapp.com/developer/user-guide/sandbox-mode“Sandbox mode allows you to safely test out different parts of Postmark without accidentally sending email to real recipients.”postmarkapp.com/blog/new-in-postmark-sandbox-mode“Here's a safe space for you to experiment with Postmark—without the risk of accidentally sending test mail to real customers.”

SDK languages

Python, Node.js, PHP, .NET, Ruby, Rails, Java [14]postmarkapp.com/developer“API reference. Get straight to the details of every HTTP request available through Postmark's REST API.”

MCP server

✓ Yes [15]postmarkapp.com/lp/mcp“Postmark's MCP Server allows AI tools like Claude Desktop and Cursor to securely access and manage your Postmark emails through natural language commands.”postmarkapp.com/updates/postmark-labs-new-mcp-server-for-ai-powered-email“The MCP server exposes four core Postmark capabilities as tools that AI assistants can use directly: Send emails - Single transactional emails”

SOC 2

None [16]postmarkapp.com/support/article/is-postmark-secure-and-redundant“A DuPont Fabros facility, the Deft data center is SOC 2 Type 2 accredited and includes keycard protocols, biometric scanning protocols”postmarkapp.com/eu-privacy“The data centers we use demonstrate ongoing compliance with rigorous international standards, such. SOC 1, SOC 2, and SOC”postmarkapp.com/dpa“We host our servers in highly secure, SOC 2 certified data centers and use the latest security practices to protect our customers' data.”

HIPAA

– Unknown [17]postmarkapp.com/security“We host our servers in a secure data center and use the latest security practices.”

GDPR

✓ Yes [18]postmarkapp.com/support/article/1218-gdpr-faq“The data centers we use demonstrate ongoing compliance with rigorous international standards, such as ISO 27017 for cloud”postmarkapp.com/dpa“We host our servers in highly secure, SOC 2 certified data centers and use the latest security practices to protect our customers' data.”postmarkapp.com/eu-privacy“The data centers we use demonstrate ongoing compliance with rigorous international standar”

ISO 27001

– Unknown [19]postmarkapp.com/eu-privacy“The data centers we use demonstrate ongoing compliance with rigorous international standards, such. SOC 1, SOC 2, and SOC 3, PCI DSS Level 1, and mor”postmarkapp.com/support/article/1218-gdpr-faq“The data centers we use demonstrate ongoing compliance with rigorous international standards, such as ISO 27017 for cloud”

PCI DSS

✗ No [20]postmarkapp.com/security“We host our servers in a secure data center and use the latest security practices. Postmark gives you detailed user permissions so you certified as a PCI Level”postmarkapp.com/eu-privacy“The data centers we use demonstrate ongoing compliance with rigorous international standards, such. SOC 1, SOC 2, and SOC 3, PCI DSS Level 1, and mor”

Published SLA

✗ No [21]postmarkapp.com/terms-of-service“These Terms of Service are for new customers effective immediately as of December 10, 2024.”

Rate limits

No specific numeric rate limits published for the Email API (429 error code exists); SMTP recommended: "10 concurrent connections per IP"; Status API: "10 requests per second" [22]postmarkapp.com/developer/api/overview“429 — Rate Limit Exceeded We have detected that you are making requests at a rate that exceeds acceptable use of the API. You should reduce the rate at”status.postmarkapp.com/api“rate limiting to 10 requests per second”postmarkapp.com/support/article/do-we-have-rate-limits-for-smtp“We recommend that customers limit the total number of connections to our SMTP endpoint to 10 concurrent connections, per IP.”

Known restrictions

10 MB payload size for the standard Email API; 50 MB total for the Batch Email API, Maximum of 500 messages per batch request, Maximum of 100 templates per Server, Maximum of 10 message streams per Server, Only one inbound stream allowed per Server, Cannot send to recipients marked 'inactive' due to hard bounces or complaints, Public domains cannot be used for Sender Signatures, Spam complaint rate must be lower than 0.1% (1 in 1,000 emails), Bounce rate must be lower than 10% of all emails sent, Webhook URL cannot contain internal IP ranges [23]postmarkapp.com/developer“API reference. Get straight to the details of every HTTP request available through Postmark's REST API.”postmarkapp.com/developer/api/email-api“This endpoint is solely responsible for sending emails with Postmark through a specific server. Please note that the batch endpoint accepts up to 500 messages”

• Docs
• llms.txt
• Status page

Docs rendering: static

API style

rest

Base URL

https://api.postmarkapp.com

Versioning

none

Stability

ga

Auth methods

api_key

Idempotency keys

✗ No

Error format

vendor-specific

SDKs

• Python postmark-python (PyPI) · repo · updated 2026-06 · 12★
• Node.js postmark (npm) · repo · updated 2026-05 · 358★
• PHP wildbit/postmark-php (Composer) · repo · updated 2026-01 · 176★
• .NET Postmark (NuGet) · repo · updated 2026-01 · 54★
• Ruby postmark (RubyGems) · repo · updated 2024-07 · 228★
• Rails postmark-rails (RubyGems) · repo · updated 2024-09 · 394★
• Java com.postmarkapp:postmark (Maven) · repo · updated 2026-03 · 43★

• Auth docs
• Quickstart
• MCP server
• Webhook events

Launched

2009-01-01

Notable customers

LiveChat, Asana, IKEA, UNICEF, 1Password, Paddle, Webflow, InVision, Wistia, Betterment, Moz, VSCO, Mastodon, Mojang, Litmus, Livestream, Desk

• Mailgun

  Mailgun is the all-in-one, intelligent email delivery platform trusted by businesses and loved by developers.

  Hybrid · free tier · public pricing · self-serve

• Mailjet

  The best email marketing software that's built for devs and loved by marketers.

  Hybrid · free tier · public pricing · self-serve

• Amazon Simple Email Service

  Amazon Simple Email Service (Amazon SES) is a cloud-based email service provider that can integrate into any application for high-volume email automation.

  Usage · public pricing · self-serve

• Brevo

  Brevo is the most intuitive all-in-one customer engagement platform: email and SMS marketing, automation, CRM, live chat, and transactional email.

  Hybrid · free tier · public pricing · self-serve

• SendGrid

  Email at scale, proven deliverability, and so much more

  Hybrid · public pricing · self-serve

• MailerSend

  MailerSend is a powerful transactional email system built for developers but designed so non-tech teams can contribute without coding.

  Hybrid · free tier · public pricing · self-serve

Postmark alternatives · Postmark vs Mailgun · All Email APIs APIs

Each field above carries a numbered source - hover for a preview, click to jump here.

1. ↑Description: postmarkapp.com
2. ↑Pricing model: postmarkapp.com · postmarkapp.com · buildmvpfast.com
3. ↑Published pricing: postmarkapp.com
4. ↑Free tier: account.postmarkapp.com · postmarkapp.com
5. ↑Free tier details: account.postmarkapp.com · postmarkapp.com
6. ↑Self-serve signup: account.postmarkapp.com
7. ↑Requires sales call: account.postmarkapp.com
8. ↑Enterprise plan: postmarkapp.com
9. ↑Supported actions: postmarkapp.com · postmarkapp.com · postmarkapp.com
10. ↑Input types: postmarkapp.com
11. ↑Output types: postmarkapp.com · postmarkapp.com
12. ↑Webhooks: postmarkapp.com · postmarkapp.com · postmarkapp.com
13. ↑Sandbox: postmarkapp.com · postmarkapp.com
14. ↑SDK languages: postmarkapp.com
15. ↑MCP server: postmarkapp.com · postmarkapp.com
16. ↑SOC 2: postmarkapp.com · postmarkapp.com · postmarkapp.com
17. ↑HIPAA: postmarkapp.com
18. ↑GDPR: postmarkapp.com · postmarkapp.com · postmarkapp.com
19. ↑ISO 27001: postmarkapp.com · postmarkapp.com
20. ↑PCI DSS: postmarkapp.com · postmarkapp.com
21. ↑Published SLA: postmarkapp.com
22. ↑Rate limits: postmarkapp.com · status.postmarkapp.com · postmarkapp.com
23. ↑Known restrictions: postmarkapp.com · postmarkapp.com

Every field change, who made it, and when - from our audited data pipeline and editors.

1. 2026-06-15 Score Agent Friendliness: 55 → 60
2. 2026-06-15 Score Docs Quality: 25 → 15
3. 2026-06-15 Has Structured Data: (none) → Yes
4. 2026-06-15 Llms Txt Present: Yes → No
5. 2026-06-15 Robots Allows Agents: (none) → Yes
6. 2026-06-09 Best For: Prototypes and side projects — free to start, no sales call, AI agents and auto… → Prototypes and side projects - free to start, no sales call, AI agents and auto…
7. 2026-06-09 Scoring Methodology: Scores are computed deterministically from this profile's published, sourced fi… → Scores are computed deterministically from this profile's published, sourced fi…
8. 2026-06-09 Score Setup Speed: (none) → 100
9. 2026-06-09 Score Agent Friendliness: (none) → 55
10. 2026-06-09 Score Pricing Transparency: (none) → 100
11. 2026-06-09 Avoid If: (none) → You have strict compliance requirements
12. 2026-06-09 Best For: (none) → Prototypes and side projects — free to start, no sales call, AI agents and auto…
13. 2026-06-09 Scoring Methodology: (none) → Scores are computed deterministically from this profile's published, sourced fi…
14. 2026-06-09 Score Trust Readiness: (none) → 15
15. 2026-06-09 Score Procurement Friction: (none) → 100
16. 2026-06-09 Score Docs Quality: (none) → 25
17. 2026-06-08 Llms Txt URL: (none) → https://postmarkapp.com/llms.txt
18. 2026-06-08 Llms Txt Present: (none) → Yes
19. 2026-06-08 Docs URL: (none) → https://developer.postmarkapp.com
20. 2026-06-08 Status Page URL: (none) → https://status.postmarkapp.com
21. 2026-06-08 Rendering: (none) → static
22. 2026-06-07 SDK Packages: Python, Node.js, PHP, .NET, Ruby, Rails, Java → Python, Node.js, PHP, .NET, Ruby, Rails, Java
23. 2026-06-07 Summary Md: (none) → Postmark is a transactional email service focused on fast, reliable delivery fo…
24. 2026-06-07 SDK Languages: Python, Ruby, .NET, Java, PHP, Node.js → Python, Node.js, PHP, .NET, Ruby, Rails, Java
25. 2026-06-07 Fields Not Found: (none) → ga_date
26. 2026-06-07 Notable Customers: (none) → LiveChat, Asana, IKEA, UNICEF, 1Password, Paddle, Webflow, InVision, Wistia, Be…
27. 2026-06-07 Launched At: (none) → 2009-01-01
28. 2026-06-07 Free Tier Limit: (none) → 100 emails/month
29. 2026-06-07 Auth Docs URL: (none) → https://postmarkapp.com/developer/api/overview
30. 2026-06-07 Auth Methods: (none) → api_key
31. 2026-06-07 Price Basis: (none) → month
32. 2026-06-07 Starting Price Usd: (none) → 15
33. 2026-06-07 Data Retention Policy URL: (none) → https://postmarkapp.com/support/article/how-long-are-inbound-and-outbound-messa…
34. 2026-06-07 Requires Verification: (none) → Yes
35. 2026-06-07 Webhook Events URL: (none) → https://postmarkapp.com/developer/webhooks/webhooks-overview
36. 2026-06-07 Error Format: (none) → vendor-specific
37. 2026-06-07 Idempotency Supported: (none) → No
38. 2026-06-07 Quickstart URL: (none) → https://postmarkapp.com/developer/user-guide/send-email-with-api
39. 2026-06-07 MCP URL: (none) → https://github.com/ActiveCampaign/postmark-mcp
40. 2026-06-07 SDK Packages: Python, Ruby, .NET, Java, PHP, Node.js → Python, Node.js, PHP, .NET, Ruby, Rails, Java
41. 2026-06-07 Stability: (none) → ga
42. 2026-06-07 Versioning Scheme: (none) → none
43. 2026-06-07 Base URL: (none) → https://api.postmarkapp.com
44. 2026-06-07 API Style: (none) → rest
45. 2026-06-07 SDK Packages: (none) → Python, Ruby, .NET, Java, PHP, Node.js
46. 2026-06-07 Capabilities: {"smtp":true,"inbound":true,"analytics":true,"marketing":true,"templates":true,… → {"smtp":true,"inbound":true,"analytics":true,"marketing":true,"templates":true,…

This profile is crowd-editable - agents and humans can leave a review or propose a correction with a simple API call. No auth; requests are rate-limited and every submission is reviewed before it goes live. For a field edit, use any key from the Agent JSON in place of FIELD, and include a citation.

curl -X POST https://apio.sh/api/feedback/postmark \
  -H 'Content-Type: application/json' \
  -d '{"kind":"review","rating":5,"body":"Your experience with this API…"}'

curl -X POST https://apio.sh/api/suggest/postmark/FIELD \
  -H 'Content-Type: application/json' \
  -d '{"value":"corrected value","citations":[{"url":"https://source.example/page","excerpt":"supporting quote"}],"note":"what changed and why"}'

All the ways to contribute →