Overview
GSendr is a multi-tenant campaign platform built at G6 Labs Asia for organizations that need Official WhatsApp Cloud API and personalised bulk email in one place — not as bolt-ons.
An org uploads an audience once, sends on WhatsApp, email, or both, proves delivery, and catches WhatsApp replies in a shared reply desk with the originating campaign already attached. Today roughly 10 organizations run on the platform, collectively sending on the order of 10K+ WhatsApp messages and 10K+ emails on a busy day.
I owned the full stack: Next.js (App Router) + TypeScript on the front, Express.js + PostgreSQL on the API, Meta’s WhatsApp Cloud API for template campaigns, Resend for verified-domain email, Chart.js for engagement views, and Zod across validation boundaries.
The problem
Most “omnichannel” tools treat WhatsApp as an afterthought:
- Email and WhatsApp audiences diverge — ops ends up maintaining two lists.
- Replies land in a generic inbox with no link back to the campaign that started the thread.
- Bulk email personalisation stops at merge tags; finance and ops still need per-recipient PDFs (statements, invoices, policies).
- Multi-org SaaS needs hard tenancy: templates, domains, numbers, and analytics scoped per organization.
GSendr treats both channels as first-class, and treats conversation as part of the campaign lifecycle.
What I built
Official WhatsApp Cloud API
We didn’t start here. Early GSendr sent via Evolution API (unofficial). Even with working-hour windows, daily caps, and send delays, numbers were getting banned fast — a non-starter for multi-org customers. We migrated to Meta’s Official Cloud API with approved templates: template governance per org, bulk pipelines with retries and failure states, and delivery / read / failed signals in campaign reporting. Reliable, attributable outbound — not a grey-route blast.
One audience, two channels
The same recipient pipeline feeds WhatsApp and email. Import, validation, and targeting sit in one place; channel choice is a send decision, not a data-model fork. Teams don’t maintain parallel lists just because the channel changed.
Personalised bulk email + PDFs
For campaigns that need attachments, GSendr generates HTML → PDF per recipient matched to spreadsheet rows, then sends via verified-domain flows (SPF/DKIM/DMARC-aware). Opens, clicks, and bounces land back on the campaign so ops can see what actually happened.
Shared reply desk
WhatsApp replies open Meta’s 24-hour customer-service window. The desk keeps conversations tied to the campaign that started them, so agents aren’t guessing which blast a customer is responding to. Free-form replies stay inside that window; campaign context stays intact.
Multi-tenant by default
Organizations, teams, domains, templates, and analytics are scoped. That matters once you’re not one company with one number — you’re a platform running concurrent campaigns for different orgs without leaking audiences or credentials.
Features
- Official WhatsApp Cloud API — Meta-approved templates, bulk WhatsApp campaigns, delivery/read tracking, multi-org sending
- Shared WhatsApp reply desk — campaign-linked conversations with free-form replies inside the 24-hour window
- Personalised bulk email — HTML-to-PDF per recipient matched to spreadsheet rows in one campaign
- Multi-tenant organization model with scoped resources and teams
- Campaign lifecycle from draft to schedule/send with status controls
- Domain verification, sender identity, and deliverability governance
- Recipient import, validation, and engagement analytics (delivered, opened, clicked, bounced, WhatsApp read/failed)
Results
In production across ~10 organizations:
- Sustained daily volume on the order of 10K+ WhatsApp and 10K+ emails
- Unified WhatsApp + email on one audience with campaign-linked reply handling
- Personalised attachments and verified-domain sending with engagement analytics
- Multi-tenant ops without artificial daily send-cap bottlenecks
Roadmap
- Live — Email campaigns with verified-domain sending, personalised attachments, and engagement analytics
- Live — Official WhatsApp Cloud API campaigns, templates, and shared reply desk at current multi-org volume
- In development — AI Reply that drafts on-brand WhatsApp responses from campaign + conversation context
- Planned — Voice Blast, SMS, deeper audience segmentation and lifecycle automation, expanded deliverability diagnostics, stronger org-level policy/compliance controls
Related
- How we built GSendr — architecture, audiences, PDFs, reply desk, tenancy
- Why we left Evolution API — unofficial WhatsApp, bans, and the move to Official Cloud API