MailSense-AI

A Gmail extension plus Spring Boot backend that drafts email replies with Google Gemini. Pick a tone, or use My Tone, which retrieves your own past emails (RAG) so drafts sound like you.

Features

• Generate Reply button inside Gmail, next to Send, with a tone dropdown
• Preset tones: professional, casual, friendly, concise, empathetic, neutral
• My Tone: retrieval-augmented generation over your own sent emails
• Retries and a fallback model when Gemini is overloaded
• Training page to add your emails: http://localhost:8080/train.html

Architecture

Gmail (content.js) --> POST /api/email/generate --> EmailGeneratorService
                                                     |-- preset tone: build prompt
                                                     '-- My Tone: embed email -> top-5 similar
                                                         past emails -> few-shot prompt
                                                                   |
                                             Gemini generateContent (retry + fallback)
Training: train.html --> POST /api/style/ingest --> embeddings --> style-store.json

How My Tone works

1. Each email you save is embedded (gemini-embedding-001, 768 dimensions) and stored locally in style-store.json.
2. For a new email, the backend embeds it and finds the 5 most similar saved emails by cosine similarity (exact search, in memory).
3. Those emails go into the prompt as style examples, and Gemini writes the reply.

This is basic RAG, used to retrieve style examples, not facts. No vector database is needed at this scale.

Tech stack

Java 21, Spring Boot 3.5, Maven, WebClient, Jackson, Lombok / React (Vite) / Chrome Extension (Manifest V3) / Google Gemini API

Setup

Backend

1. Install JDK 21.
2. Get a key from Google AI Studio.
3. Set it as an environment variable (never commit it): GEMINI_KEY=your_key
4. Run MailSenseAiApplication (or ./mvnw spring-boot:run from the backend folder).

Extension

1. Open chrome://extensions and enable Developer mode.
2. Click Load unpacked and select the mailsense-ext folder.
3. Open Gmail, click Reply, and use the button next to Send.

My Tone

1. Open http://localhost:8080/train.html.
2. Paste emails you wrote, separated by a line containing only --, and save.

API

Method	Path	Purpose
POST	/api/email/generate	{emailContent, tone} returns the reply text
POST	/api/style/ingest	{emails: [...]} embeds and saves samples
GET	/api/style/count	number of saved samples
DELETE	/api/style	delete all saved samples

Privacy

Your emails are sent to Google's API for embedding and inside prompts. Samples are stored locally in style-store.json, which is git-ignored. Don't paste anything sensitive.

Known limitations

• Runs on localhost only, and the API has no authentication (local use only)
• Exact brute-force search over a JSON file; suitable for hundreds of emails, not millions
• Retrieval is by topic similarity, not writing style
• Gmail's page structure changes, so selectors may need updating
• No automated evaluation of draft quality yet

Roadmap

• Store (email received, reply sent) pairs instead of replies only
• Evaluation: compare drafts to real replies
• pgvector and per-user auth for multi-user use
• Route requests through the extension's background worker and restrict CORS