Build an Innovative Email SaaS Platform

We want a SaaS platform where customers can add their own SMTP/relay servers (or provide credentials/APIs) and pool multiple servers into sending groups. The platform should manage warm-up automation (auto replies, slow ramp-up), coordinate cross-server test traffic, monitor deliverability and reputation, automatically handle bounces, DKIM/SPF/DMARC, run blacklist checks, and provide dashboards, analytics, and APIs. The platform must prevent abuse, enforce opt-in/consent rules, and include billing, multi-tenant isolation, logging, and alerting.

Goals

1. Let customers add/manage multiple sending servers and group them into pools.


2. Provide automated warm-up workflows (progressive send quotas, auto-reply loop tests to warm IPs/domains).


3. Maximize inbox delivery via monitoring, feedback loops, suppression lists, blacklist checks, and reputation scoring.


4. Full observability: dashboards, logs, alerts, per-server/per-pool metrics (delivery, bounce, complaint, open, click).


5. Provide API + web UI for campaign scheduling, templates, and programmatic control.


6. Strong anti-abuse/compliance features and secure infrastructure.



Target Users

Email marketing operators with their own mail servers

Agencies managing multiple client servers

Enterprises that want better deliverability and warm-up

Developers wanting API-based sending with deliverability features



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Core Features (by priority)

1. Server onboarding & management

Add SMTP servers (host, port, username, password), API-based relays (SendGrid, Mailgun, Amazon SES, etc.), or self-hosted gateways.

Validate ownership before sending: required DNS verification steps (add TXT record), or return-path verification.

Manage DKIM keys, SPF records instructions, and DMARC reporting integration.

Tag servers (region, provider, IP type: shared/dedicated).


2. Pools & routing

Create pools (groups of servers) with weight-based routing, round-robin and failover options.

Send campaigns via a selected pool; system handles server selection, retries, and per-server throttling.

Smart routing modes: deliverability-first (avoid servers with bad reputation), cost-first (prefer cheaper relays).


3. Warm-up automation

Automated warm-up plan builder: configure target daily volume, ramp schedule, sending cadence, recipient selection for intra-pool warm-up tests.

Auto-reply simulator: orchestrate controlled replies between verified partner inboxes to build positive signals (only between consenting/verified domains).

Automatic suppression of warm-up recipients from production campaigns.


4. Deliverability & Inbox placement improvements

Real-time metrics: delivery rate, bounce types, complaint rate, spam trap hits, open/click rates.

Inbox placement heuristics and deliverability scoring per server/IP/domain.

Integrate ISP feedback loops where possible (e.g., AOL/Yahoo complaints).

Blacklist / DNSBL monitoring with automated alerting and guidance.


5. Bounce & complaint handling

Parse bounces (hard/soft), classify them, auto-suppress or retry according to rules.

Maintain global & tenant-level suppression lists and unsubscribes.

Complaint tracking and immediate throttling/pausing of offending campaigns.


6. Compliance & anti-abuse

Required domain ownership verification and identity checks for onboarding.

Mandatory consent/opt-in capture; provide templates/landing pages to collect proof of consent.

Rate limits, per-tenant reputation thresholds, automated blocks for spikes or suspicious behavior.

Admin dashboard for abuse reports, manual shutdown of tenant servers.


7. UI & UX

Admin (platform owner) console: tenant management, overall health, billing, abuse dashboard.

Tenant dashboard: servers, pools, campaigns, templates, warm-up manager, analytics.

Campaign composer: template editor, personalization macros, scheduling, A/B testing.


8. API & integrations

RESTful API for: adding servers, creating pools, sending messages, campaign status, suppression management, and webhooks for events (deliveries, bounces, complaints).

Webhooks and SNMP/Prometheus for metrics and alerts.

Optional connector for common CRMs and ESPs.


9. Security, logging & auditing

Audit logs for administrative actions & sending events.

Encryption-at-rest for credentials, rotateable secrets.

Role-based access control (RBAC) for tenants.

Rate limit & per-IP connection controls.


10. Billing & multi-tenant

Tiered billing: per-sender (per server) and usage-based (sent messages, relays used).

Payment integrations (Stripe, PayPal).

Invoices, usage reports, and trial management.



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Non-functional Requirements

Scalable: support thousands of servers and millions of messages/day.

Highly available: failover and retries, stateless workers where possible.

Observability: metrics exported to Prometheus/Grafana; logs (elastic stack or similar).

Privacy compliant: GDPR, data residency options if needed.

Secure: HTTPS everywhere, vault for secrets (HashiCorp Vault or cloud KMS).



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Suggested Tech Stack (recommendation; open to alternatives)

Backend: Node.js (NestJS) or Python (FastAPI) or Go for performance-critical parts.

Queue / workers: RabbitMQ, Redis Queue, or Kafka for large scale.

Email worker library: custom SMTP client + retry logic; built-in support for API relays.

Database: PostgreSQL for primary data; Redis for caching/locks.

Storage: S3-compatible for attachments/logs.

Infrastructure: Docker + Kubernetes (EKS/GKE/AKS) for scale.

Monitoring: Prometheus + Grafana, ELK/Opensearch for logs.

Secrets: HashiCorp Vault or cloud KMS.

CI/CD: GitHub Actions / GitLab CI.

Frontend: React + Tailwind (or Next.js) for dashboards.

Optional: ClickHouse for analytics if high-volume event storage needed.



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Data Model — high level

Tenants (customers)

Servers: id, owner_tenant, host, port, auth, verification_status, DKIM_key, IPs

Pools: id, tenant_id, server_ids, routing_policy

Campaigns: id, pool_id, template, schedule, recipient_list_id, stats

Recipient lists: id, tenant_id, verified_consent_proof

Events: deliveries, bounces, complaints, opens, clicks (event store)

Suppression lists: global and tenant-specific

Audit logs: actor, action, timestamp



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API Endpoints (examples)

POST /api/v1/servers — add server (returns verification steps)

POST /api/v1/servers/{id}/verify — submit proof / check DNS

POST /api/v1/pools — create pool

POST /api/v1/campaigns — create campaign

POST /api/v1/send — send a single transactional message (via pool)

GET /api/v1/metrics/pool/{id} — get deliverability stats

POST /api/v1/webhooks/events — receive bounce/delivery webhooks



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Security & Anti-Abuse Controls (must-have)

1. Domain/SMTP verification required before any production sending.


2. Daily/Hourly quota and progressive ramp-up defaults.


3. Automated spike detection — pause & notify if sudden surge.


4. Mandatory unsubscribe header support & suppression enforcement.


5. Manual review or KYC for high-volume accounts.


6. Abuse takedown process with required evidence retention.




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Acceptance Criteria (must pass to be accepted)

Servers can be onboarded and verified with DKIM/SPF/DMARC instructions and verification flow.

Pools can be created and tested; messages can be routed through chosen pool with failover.

Warm-up automation runs according to a schedule; system demonstrates progressive ramping and auto-reply interactions between consenting mailboxes.

Bounces / complaints are parsed and classified; suppressed accordingly.

Dashboard shows real-time metrics (delivery, bounce, complaints, opens).

API endpoints documented and tested; sample client demonstrates end-to-end send and event handling.

Security checks in place (credential encryption, RBAC, audit logs).

Anti-abuse rules operate: suspicious account is automatically paused and flagged.

Basic billing flow implemented and invoices generated.