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Postmark vs Substack
Postmark: Developers needing fast, reliable transactional email. Substack: Writers making money doing the work they believe in. Same fact set for both, straight from each vendor's docs.
Postmark
- Free tier
- Free developer plan: 100 emails/mo, never expires
- Paid from
- $15/mo (Basic, 10,000 emails) · pricing page
- Public API
- Yes docs
- MCP server
- Yes · Official MCP server (ActiveCampaign/postmark-mcp), 24 tools
- Best for
- Developers needing fast, reliable transactional email
- Website
- https://postmarkapp.com
Substack
- Free tier
- Free to publish, no subscriber cap
- Paid from
- No monthly fee; 10% of paid subscription revenue plus Stripe fees · pricing page
- Public API
- Yes docs
- MCP server
- Community · Community servers on GitHub only
- Best for
- Writers making money doing the work they believe in
- Website
- https://substack.com
Which one?
Postmark suits developers needing fast, reliable transactional email. Substack suits writers making money doing the work they believe in. Pricing changes; the fact tables above link both vendors' live pricing pages. For the rest of the field, see Postmark alternatives, Substack alternatives, or the full table.