Building Senduta: A Digital Courier That Proves Your Document Was Actually Opened

Viswa Prathap — Fri, 03 Jul 2026 11:04:15 +0000

WeTransfer tells you a file was sent. Email tells you a message was delivered, maybe. Neither tells you the one thing that actually matters when you're sending a signed contract, a legal notice, or a client's financial records: did the right person actually open it?

That gap is what we're building Senduta to close — a secure digital courier for confidential documents, built for lawyers, chartered accountants, recruiters, consultants, and architects who need something closer to registered post than a share link.

The problem with "just send it as an attachment"

Most document sharing today optimizes for convenience, not accountability:

Email attachments can be forwarded infinitely, with zero record of who opened them.
Generic file-transfer tools confirm upload, not delivery.
Nobody produces a certificate you could actually hand to a court or a compliance auditor.

For a lawyer serving a notice or a CA sharing financials, "I think they got it" isn't good enough.

What Senduta does differently

Senduta treats every send like a courier parcel, not a storage bucket:

Email-OTP verification — only the intended recipient can unlock the file
Full audit trail — delivered → opened → downloaded, each with timestamp, IP, and device
Certified delivery PDF — a branded certificate with a SHA-256 integrity hash of the file
AES-256 encryption in transit and at rest, plus dynamic watermarking
Self-destruct — files are permanently deleted 24 hours after download
Link expiry & instant revoke, resumable uploads up to 50GB

The self-destruct part is deliberate: Senduta is a courier, not a storage service. It delivers, then deletes — which also means we're not sitting on a growing pile of other people's confidential documents.

The stack

Nothing exotic — mostly boring, reliable choices so we can move fast without fighting the tools:

Next.js 16 / React 19 for the app
Supabase for auth, Postgres, and session state
AWS S3 (via @uppy/aws-s3 for resumable multipart uploads) for file storage — since files are transient, S3 with lifecycle rules made more sense than baking storage assumptions into the DB layer
Resend for transactional email (OTP codes, delivery notifications)
pdf-lib to generate the certified delivery PDFs server-side, embedding the SHA-256 hash at generation time
sharp for watermarking and image processing
Claude API (Anthropic SDK) — this is the part I'm most excited about. We're layering in AI-assisted document summaries and smart tagging on top of the delivery pipeline, so recipients (and senders) get a quick sense of what's inside a document before committing to a full read

What's next

We're mid-build across a staged roadmap: core send/receive flow and audit logging are in place, and we're working through OTP gating, watermarking, and the certificate/hash pipeline before layering the Claude-powered document intelligence on top.

If you send confidential documents for a living — or you're just interested in the "prove it, don't just trust it" approach to document delivery — I'd love feedback. Follow along at senduta.com.

Building in India, for the world.

DEV Community: Viswa Prathap

Building Senduta: A Digital Courier That Proves Your Document Was Actually Opened

The problem with "just send it as an attachment"

What Senduta does differently

The stack

What's next