Features
SMTP relay for auth providers and legacy apps
Keep clients that only speak SMTP — Supabase hooks, Clerk-style providers, older apps — on the same SuperSend TX account as your HTTP API.
- Port 587 with STARTTLS
- Rotatable credentials
- Shared suppressions with HTTP
Why SMTP
Not every stack wants a REST client
Auth tools, CMSes, and internal apps often expect host, port, username, and password. Meet them there.
Drop-in config
Point any SMTP client at our relay — no SDK, no rewrite, no proxy layer.
One safety model
Verified domains, plan limits, and suppressions behave exactly like the HTTP API.
Managed credentials
Create and revoke SMTP passwords in the dashboard or over the API.
Rotate safely
Swap credentials without touching DNS or reverifying your domains.
How it works
Connected in four steps
Same onboarding as the API: verify the domain first, then hand credentials to your client.
- 1
Verify a domain
Add your sending domain and complete DNS verification.
- 2
Create a credential
Generate an SMTP password (stxsmtp_…) in the dashboard.
- 3
Point your client
Use smtp.supersendtx.com on port 587 with STARTTLS.
- 4
Send
From-domain rules, limits, and suppressions apply automatically.
Connection
The only settings you need
Anything that can send SMTP can send through SuperSend TX.
- Works alongside the API, SDKs, CLI, and webhooks
- Failed SMTP sends feed the same suppression list
- Great fit for Supabase Auth and similar providers
SMTP settings
Host: smtp.supersendtx.com
Port: 587 (STARTTLS)
Username: supersendtx
Password: stxsmtp_…
# From must use a verified domain
From: [email protected]- · Revoke or rotate credentials any time
- · Prefer HTTP for Supabase? See the integration guide
At a glance
Same platform, different transport
Host
smtp.supersendtx.com
STARTTLS on 587
Auth
stxsmtp_…
dashboard managed
Domains
Shared
same verification as API
Suppressions
Shared
bounces and complaints
Send over SMTP without giving up control
Create a credential, point your client at port 587, and keep every guardrail you already have.