Email Marketing Automation in 2026: 5 Tools (and 1 Self-Hosted) Through Their APIs (opens in new tab)

I've wired up email automation in 5 different SaaS products over the last 3 years. Every time the team asks "Mailchimp or…?" — and every time the right answer depends on whether you actually need marketing campaigns, transactional sends, or both. This post is the version of that conversation aimed at people who'd rather see a curl than a pricing table. The decision tree What are you sending? ├── Transactional only (receipts, password resets, magic links) │ → Resend / Postmark / SES (skip the ...