Question 1

What is Posta?

Accepted Answer

Posta is a private, secure mail system exclusively for @subhr.in addresses. It uses a custom C backend server, Clerk authentication with RS256 JWT verification via OpenSSL, and PostgreSQL database isolation for maximum privacy and security.

Question 2

Who can use Posta?

Accepted Answer

Posta is exclusively for @subhr.in domain users. Only addresses ending in @subhr.in can send and receive mail within this closed network.

Question 3

How does Posta ensure privacy?

Accepted Answer

Posta uses zero-trust architecture: the Next.js frontend has zero database credentials or access. All mail traffic routes through a custom C server that validates Clerk JWT sessions using OpenSSL RS256 verification. Database is completely isolated from the web.

Question 4

What authentication does Posta use?

Accepted Answer

Posta uses Clerk authentication with RS256 JWT signatures verified by the C backend via OpenSSL. No shared secrets, no token forwarding - cryptographic verification at the edge.

Question 5

How does email delivery work?

Accepted Answer

Incoming SMTP traffic flows on port 2525. A background database-driven worker manages queue status, retry logic, and delivery confirmation for both SMTP and web submissions. SMTP and web share one async queue pipeline.