Every listing carries the same fields in the same order. Counts beside each filter update as you narrow.
| API | Pricing | Auth | Format | Free tier | Status |
|---|---|---|---|---|---|
Atomic MailSelf-registers a real email inbox for an AI agent (PoW, no signup) and sends/receives mail via JMAP. Communication › Email | Free | API key | JSON | Unlimited | Live |
BrevoSend transactional and marketing email, SMS and WhatsApp, and manage contacts via one REST API. Communication › Email | Freemium | API key | JSON | 100–1k/day | Live |
Email Spam TesterSends a test email through 42 deliverability and spam checks, then returns a scored JSON report. Communication › Email | Free | None | JSON | <100/day | Untested |
EmailJSSends transactional emails from client-side JavaScript without a backend server. Communication › Email | Freemium | API key | JSON | <100/day | Untested |
ImprovMXManages email forwarding aliases and SMTP sending credentials for a custom domain. Communication › Email | Freemium | API key | JSON | 10k+/day | Live |
IndiePitcherSends transactional emails with markdown support and manages contact lists for SaaS apps Communication › Email | Freemium | API key | JSON | <100/day | Live |
MailjetTransactional and marketing email sending, contact list management, and delivery stats via REST API. Communication › Email | Freemium | API key | JSON | 100–1k/day | Live |
MailtrapTransactional and bulk email sending API with a built-in sandbox for safely testing emails. Communication › Email | Freemium | API key | JSON | 100–1k/day | Untested |
PostStackEU-hosted transactional and marketing email sending with templates, broadcasts and webhooks. Communication › Email | Freemium | API key | JSON | 100–1k/day | Live |
ResendSends transactional and marketing emails from your app via a REST API with domain verification. Communication › Email | Freemium | API key | JSON | 100–1k/day | Live |
SendGridTransactional and marketing email delivery API with templates, webhooks, and delivery analytics. Communication › Email | Free trial | API key | JSON | — | Untested |
SMTPfastSends transactional email and manages contacts, segments and broadcast campaigns via a REST API. Communication › Email | Freemium | API key | JSON | 100–1k/day | Live |
Atomic MailFreeLive
Self-registers a real email inbox for an AI agent (PoW, no signup) and sends/receives mail via JMAP.
API key · JSON
Unlimited
llms.txt
BrevoFreemiumLive
Send transactional and marketing email, SMS and WhatsApp, and manage contacts via one REST API.
API key · JSON
100–1k/day
llms.txt
Email Spam TesterFreeUntested
Sends a test email through 42 deliverability and spam checks, then returns a scored JSON report.
None · JSON
<100/day
llms.txt
EmailJSFreemiumUntested
Sends transactional emails from client-side JavaScript without a backend server.
API key · JSON
<100/day
no machine-readable spec
ImprovMXFreemiumLive
Manages email forwarding aliases and SMTP sending credentials for a custom domain.
API key · JSON
10k+/day
llms.txt
IndiePitcherFreemiumLive
Sends transactional emails with markdown support and manages contact lists for SaaS apps
API key · JSON
<100/day
OpenAPI spec · llms.txt
MailjetFreemiumLive
Transactional and marketing email sending, contact list management, and delivery stats via REST API.
API key · JSON
100–1k/day
no machine-readable spec
MailtrapFreemiumUntested
Transactional and bulk email sending API with a built-in sandbox for safely testing emails.
API key · JSON
100–1k/day
MCP server · llms.txt
PostStackFreemiumLive
EU-hosted transactional and marketing email sending with templates, broadcasts and webhooks.
API key · JSON
100–1k/day
llms.txt
ResendFreemiumLive
Sends transactional and marketing emails from your app via a REST API with domain verification.
API key · JSON
100–1k/day
llms.txt
SendGridFree trialUntested
Transactional and marketing email delivery API with templates, webhooks, and delivery analytics.
API key · JSON
—
OpenAPI spec
SMTPfastFreemiumLive
Sends transactional email and manages contacts, segments and broadcast campaigns via a REST API.
API key · JSON
100–1k/day
llms.txt
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