Quick Summary 📌
MailFinch is a Google Sheets plugin that lets users send personalised emails in bulk. AirOxa built the plugin — using React, NestJS, MongoDB, Stripe & Docker — to help a client automate outreach with custom fields and templated logic.
Introduction
Bulk email tools rarely give users full control while keeping things simple. Most companies rely on separate systems or complex platforms to run email campaigns. That approach limits speed and flexibility. MailFinch solves this by working inside Google Sheets. Users select data from any spreadsheet (for names, company details, or other fields) and fire off a batch of unique, customised emails directly from the sheet — without leaving it.
MailFinch did not exist as a concept before AirOxa stepped in. AirOxa created the plugin from scratch and delivered it as a finished product to one of its clients. Even though MailFinch is no longer operational today, this MailFinch Google Sheets plugin case study breaks down how AirOxa conceptualised, built, and deployed a complete mini-SaaS around a familiar user workflow.
Strategy Behind the Build
The goal was to deliver a plugin that makes everyday users feel powerful. If someone uses Google Sheets to track contacts, they should not have to move into another tool just to send emails. Instead of forcing new behaviours, MailFinch adapts to what users already do.
AirOxa designed MailFinch to:
- Show up natively in the Google Sheets sidebar
- Allow the user to write a single email template
- Convert spreadsheet fields into personalised email variables
- Trigger the send inside the same sheet environment
- Respect Gmail’s sending rules and deliver emails in a controlled wave
With those outcomes in mind, AirOxa engineered the entire product lifecycle — from user interface, API design, and email logic to billing and Docker-based deployment.
Building the Google Sheets UI
AirOxa used React.js to build a front-end panel that loads inside Google Sheets as an add-on. This panel walks users through connection steps, email template drafting, previewing, and sending. Even first-time users can set up their first mail-merge-style campaign without reading any documentation.
The interface uses dropdowns that pull headings straight from the sheet. Once mapped, the user can send emails while watching the progress live. This keeps everything transparent and user-friendly.
Designing the Backend
Under the hood, NestJS powers the backend API. MongoDB stores templates, user details, send-history, and plan types. The backend enforces rate limits and handles email-sending queues so Gmail does not flag the account. Each message takes values from the spreadsheet row and replaces placeholders inside the email body.
This clear separation of concern — React for presentation and NestJS for business logic — gives MailFinch long-term maintainability and flexibility.
Handling Gmail Limits and Delivery
AirOxa uses official Gmail APIs to send emails one batch at a time. The system waits between batches, dynamically adjusting speed based on remaining daily quota. As a result, users won’t accidentally overload Gmail or suffer blocked accounts.
Rather than hiding these details, MailFinch keeps the user informed through progress indicators and post-send logs.
Payment Integration
To monetise the tool, AirOxa integrated Stripe. The plugin supports multiple plan levels (based on how many emails the user wants to send). Plan enforcement happens automatically — not manually — based on activity.
Docker for Scalable Hosting
Finally, AirOxa packaged the entire service using Docker, which simplifies deployment across environments. If the client wanted to host MailFinch on different servers or roll out updates without downtime, their team could handle it without touching core code. The container model supports version control and rollback.
Technology Behind the MailFinch Google Sheets Plugin Case Study
| Layer | Technology |
|---|---|
| Frontend | React.js |
| Backend | Nest.js |
| Database | MongoDB |
| Infrastructure | Docker |
| Billing Integration | Stripe |
Project Outcome
MailFinch turned a spreadsheet into a lightweight email-campaign machine. Users could personalise hundreds of emails and send them out without having to learn a whole new software platform. Because it sits inside Google Sheets, it feels natural — almost like a native feature rather than a third-party product.
Although the plugin is not currently live, it serves as a powerful example of how AirOxa can conceptualise and build a complete workflow tool from scratch — handling everything from UX, backend logic, API integration, and monetisation through to handoff-ready deployment.
Key Takeaway
This MailFinch Google Sheets plugin case study shows how AirOxa transforms everyday manual processes into professional-grade, scalable SaaS products. By building smart tools around how users already work — rather than forcing new behaviors — AirOxa delivers practical value that businesses can immediately use and monetise.
🚀 Inspired by the MailFinch Google Sheets Plugin Case Study?
Have a workflow or micro-SaaS idea you want to develop? AirOxa can design and build it end-to-end — exactly like we did with MailFinch.
👉 Contact us today to start building your product.