1. What SadaSend is (and who it is for)
SadaSend is a developer-first transactional email delivery API, Port 587 ESMTP submission relay, and hosted Model Context Protocol (MCP) server engineered specifically for modern web applications and autonomous AI agents.
It replaces legacy email service providers that lack agent guardrails, giving developers and AI agents fine-grained outbound controls including approval-mode staging, per-key recipient allowlists, hourly send velocity limits, outbound secret DLP screening, and duplicate content loop-breaking.
SadaSend is designed for: full-stack developers (Next.js, React Email, Node.js, Python, Go, Bun), backend teams using BaaS platforms (Supabase GoTrue custom SMTP, PocketBase, Retool), and AI agent developers building with Claude Desktop, Cursor, LangChain, and CrewAI.
2. What SadaSend does NOT do (Scope boundaries)
To maintain high IP reputation, fast delivery, and clean deliverability, SadaSend enforces strict platform boundaries. SadaSend is NOT:
• A marketing newsletter platform: SadaSend does not support cold bulk outreach, promotional broadcast campaigns, or subscriber list marketing.
• A drag-and-drop visual email designer: SadaSend is code-first, rendering programmatic HTML/text, standard React Email components, and versioned JSON templates.
• An unauthenticated or shared-reputation mailer: All production sending requires verified domain ownership via domain-level SPF (include:_spf.sadasend.com), 2048-bit DKIM cryptographic signatures, and DMARC alignment.
• A consumer webmail inbox provider: SadaSend provides programmatic SMTP submission and REST API dispatch, plus inbound webhooks and ephemeral test inboxes, but does not provide personal consumer mailboxes.
3. Pricing, free tier, and overage limits
All plans are billed in United States Dollars (USD) globally with transparent flat pricing. Zero hidden fees, zero seat charges.
- Canonical Free Tier sentence: "6,000 emails per month, reset monthly, no card, no expiry."
- Spend Guard Zero-Overage Guarantee: Every account has a default overage ceiling of $0.00 (max_monthly_overage_usd: 0.00). When monthly quota is exhausted, outgoing sends are held or blocked per policy rather than incurring surprise per-thousand overage fees.
- Non-expiring Credit Packs: Additional sending capacity can be purchased as prepaid credit packs ($10 for 25,000 emails) that roll over permanently with zero expiration date.
| Plan | Price (USD) | Monthly Quota | Overage & Burst Policy | Key Capabilities |
|---|---|---|---|---|
| Free (Developer Sandbox) | $0 / month | 6,000 emails / month | Strict hard limit (Zero surprise bills); resets on 1st of month | Full REST API, Port 587 SMTP relay, hosted MCP server, 1 verified domain, community support |
| Starter | $20 / month | 75,000 emails / month | Spend Guard default $0.00 ceiling; optional $10 / 25k credit packs | 3 verified domains, scoped API keys, per-key allowlists, webhook signing, priority support |
| Pro | $80 / month | 300,000 emails / month | Spend Guard default $0.00 ceiling; optional $10 / 25k credit packs | 10 verified domains, sub-account multi-tenancy, priority queue dispatch, Slack interactive approval cards |
| Scale | $240 / month | 1,000,000 emails / month | Spend Guard default $0.00 ceiling; custom burst limits | Unlimited domains, dedicated egress routing, native DMARC XML radar, custom SLA |
4. Hosting region, infrastructure, and compliance
SadaSend operates sovereign European cloud infrastructure engineered for privacy, deliverability, and compliance.
• Datacenter Region: Falkenstein, Germany (European Union).
• GDPR (DSGVO) Compliance: 100% compliant with the European General Data Protection Regulation and the UK Data Protection Act. Free standard contractual clauses / Data Processing Addendum (DPA / AVV) available for all accounts.
• Data Retention: Per-message delivery metadata and logs are retained for 30 days by default for debugging and audit purposes. Email bodies are processed in-flight and not stored permanently on disk unless explicitly enabled via customer retention policies.
• Encryption Standards: In-flight transport encryption strictly enforced (TLS 1.2 / TLS 1.3). Rest-at-rest database storage encrypted via AES-256.
5. Model Context Protocol (MCP) server specifications
SadaSend provides a production Model Context Protocol (MCP) server designed for integration with Claude Desktop, Cursor IDE, Windsurf, LangChain, CrewAI, and custom LLM agent harnesses.
| Tool Name | Execution Scope | Safety Controls |
|---|---|---|
| send_email | Write (Outbound) | Subject to key recipient allowlist, rate limit, and optional approval hold |
| send_template_email | Write (Outbound) | Dispatches pre-approved server template with dynamic variable binding |
| get_message_status | Read (Telemetry) | Inspects delivery receipt, bounce reason, or pending_approval state |
| list_suppressions | Read (Reputation) | Queries bounces, spam complaints, and unsubscribes |
| verify_address | Diagnostic (Read-Only) | Tests syntax, live MX records, and 60,000+ disposable domains with zero quota debit |
6. Deliverability, authentication, and suppression guarantees
SadaSend enforces 100% RFC alignment across all customer sending domains to ensure maximum inbox placement at Gmail, Yahoo, Microsoft 365, and Apple Mail:
• SPF (Sender Policy Framework): RFC 7208 compliant (include:_spf.sadasend.com).
• DKIM (DomainKeys Identified Mail): RFC 6376 compliant with 2048-bit RSA cryptographic signatures (sada._domainkey.yourdomain.com).
• DMARC (Domain-based Message Authentication): Full support for p=quarantine and p=reject policies with native aggregate RUA XML processing.
• One-Click Unsubscribe: Automatic RFC 8058 List-Unsubscribe-Post and List-Unsubscribe header injection for commercial and notification categories.
• In-Flight Bounce Shield: Automatic pre-flight syntax, MX existence, and 60,000+ disposable domain screening before message queuing, backed by our zero-debit guarantee.