Summary: Web3Forms focuses on getting an email without a backend, with a free tier that many sites never outgrow. Postbag keeps the data, routes it, signs webhooks, versions schemas and self-hosts. Different jobs; the comparison is about whether you need the record.
| Capability | Postbag | Web3Forms |
|---|---|---|
| Free tier | 5 forms, 1,000 submissions/month, 5 destinations, 90-day retention (paid plans not yet on sale) | 250 submissions/month, unlimited forms/access keys (Web3Forms pricing) |
| Entry paid | Not yet on sale | Pro $12/month or $149/year |
| Management API | Full /v1 API for every object (forms, schemas, streams, mappings, destinations, routes, deliveries, events), OpenAPI generated from the live routes | Submissions API documented; form management API not verified |
| Webhooks | Yes, HMAC-SHA256 signed (Postbag-Signature t=…,v1=…), retried with backoff, dead-lettered and retryable | Yes on Pro; signing not verified |
| Yes (Resend), Reply-To from the submission | Yes (the core product) | |
| Chat destinations | Telegram today; Slack and Discord next | Slack, Discord, Telegram |
| Spam | Honeypot, per-form rate limit, origin allowlist, Cloudflare Turnstile; spam is stored and reversible, never dropped | hCaptcha free; reCAPTCHA/Turnstile on Pro; honeypot |
| File uploads | Not yet (text fields only; 256 KB) | Pro |
| Self-hosting / source | Yes: one Docker image + Postgres, same image as the hosted product | No (client plugins are open source) |
| Schemas and drift | Versioned, immutable form and stream schemas; observe / enforce / managed modes; drift detection and inference | No |
| Many sites → one destination | Projects, tags, streams (many forms → one schema → one destination), delivery windows, digests | Agency and Team plan |
| For AI agents | llms.txt, openapi.json, GET /v1/me, POST /v1/quickstart, _test submissions with delivery ids to poll, errors with hint + docs, Idempotency-Key, if_exists: return | docs llms.txt; no MCP or CLI found |
Web3Forms facts checked on against: web3forms.com/pricing, docs.web3forms.com. Prices and quotas change; verify on their pages. Tagline quoted: "Receive form submissions directly in your email inbox without any server or back-end code".
Choose Web3Forms if
- You want email notifications for a static site and nothing else, for free.
- You need Telegram, Slack and Discord today on the free tier.
Choose Postbag if
- You need a durable record and a retryable delivery log, not just an email.
- You route to a CRM or partner and need a signed, versioned contract.
- Self-hosting or agent-driven setup matters.
What Postbag does differently, in one paragraph
Postbag treats a submission as a database row before anything else and delivery as an outbox drained by a worker, so every attempt is recorded and retryable and nothing is dropped, including spam. It adds streams, so many forms with different field names map onto one versioned schema and go to one partner or CRM with windows and digests. Every webhook is signed. The whole product is one API described by /openapi.json and /llms.txt, so an AI agent can create, verify and route a form without a browser. And it ships as one Docker image plus Postgres, so the hosted product and a self-hosted install are the same thing.