【Gemini API × docker-mailserver】AIで受信メールのフォルダ分けを自動化してみた

mkdir -p docker-data/dms/mail-data/example.com/user/.Junk/{cur,new,tmp}
mkdir -p docker-data/dms/mail-data/example.com/user/.Invoices/{cur,new,tmp}
mkdir -p docker-data/dms/mail-data/example.com/user/.JobHunting/{cur,new,tmp}
chown -R 5000:5000 docker-data/dms/mail-data/example.com/user/

mkdir classifier
vi classifier/email_classifier.py

import sys
import os
import email
import mailbox
import requests
import json
from email import message_from_bytes

# --- API キーとエンドポイント ---
API_KEY = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"  # <-- Google AI Studio から発行
ENDPOINT = f"https://generativelanguage.googleapis.com/v1beta/models/gemini-2.0-flash:generateContent?key={API_KEY}"

# --- Gemini でカテゴリ分類 ---
def classify_email(subject, body):
    prompt = f"""以下のメールを目的別に分類してください。

件名: {subject}
本文: {body}

分類カテゴリ:
- 金融取引
- 就活
- ログイン・アカウント
- 迷惑メール
- その他

カテゴリ名だけ1語で返してください。
"""

    headers = {"Content-Type": "application/json"}
    data = {
        "contents": [
            {
                "parts": [{"text": prompt}]
            }
        ]
    }

    response = requests.post(ENDPOINT, headers=headers, data=json.dumps(data))
    if response.status_code == 200:
        result = response.json()
        text = result["candidates"][0]["content"]["parts"][0]["text"].strip()
        return text if text in ["金融取引", "就活","ログイン・アカウント", "迷惑メール", "その他"] else "その他"
    else:
        print(f"Error: {response.status_code} {response.text}")
        return "その他"

# --- スパム判定 (Rspamd) ---
def is_spam(msg):
    spam_status = msg.get('X-Spam', 'no').lower()
    return spam_status == 'yes'

# --- 本文抽出 ---
def get_email_body(msg):
    body = ""
    if msg.is_multipart():
        for part in msg.walk():
            if part.get_content_type() == "text/plain":
                charset = part.get_content_charset() or "utf-8"
                body += part.get_payload(decode=True).decode(charset, errors="ignore")
    else:
        charset = msg.get_content_charset() or "utf-8"
        body = msg.get_payload(decode=True).decode(charset, errors="ignore")
    return body

# --- Maildir へ保存 ---
def move_to_mailbox(category, raw_email_bytes, recipient):
    mailbox_mapping = {
        "迷惑メール": ".Junk",
        "金融取引": ".Transactions",
        "就活": ".JobHunting",
        "ログイン・アカウント": ".Login",
        "その他": ""
    }

    local_part, domain = recipient.split("@")
    mailbox_name = mailbox_mapping.get(category, "")
    mailbox_path = f"/var/mail/{domain}/{local_part}"
    if mailbox_name:
        mailbox_path = f"{mailbox_path}/{mailbox_name}"

    msg_obj = message_from_bytes(raw_email_bytes)
    mbox = mailbox.Maildir(mailbox_path, factory=None, create=False)
    mbox.add(msg_obj)
    mbox.flush()

# --- メイン処理 ---
def main():
    raw_email_bytes = sys.stdin.buffer.read()
    msg = message_from_bytes(raw_email_bytes)

    if is_spam(msg):
        category = "迷惑メール"
    else:
        subject = msg.get("Subject", "")
        body = get_email_body(msg)
        category = classify_email(subject, body)

    recipient = sys.argv[1] if len(sys.argv) > 1 else "[email protected]"
    move_to_mailbox(category, raw_email_bytes, recipient)

if __name__ == "__main__":
    main()

    volumes:
      - ./docker-data/dms/mail-data/:/var/mail/
      - ./docker-data/dms/mail-state/:/var/mail-state/
      - ./docker-data/dms/mail-logs/:/var/log/mail/
      - ./docker-data/dms/config/:/tmp/docker-mailserver/
      - /etc/localtime:/etc/localtime:ro
      - /etc/letsencrypt:/etc/letsencrypt
      - ./classifier:/opt/classifier
      ## ↑ 追記

#!/bin/bash

# Postfix 設定ファイルの追記
TRANSPORT_FILE="/etc/postfix/transport"
MASTER_CF="/etc/postfix/master.cf"
MAIN_CF="/etc/postfix/main.cf"

# Transportマップ登録
if ! grep -q "[email protected] classifier:" "$TRANSPORT_FILE"; then
  echo "[email protected] classifier:" >> "$TRANSPORT_FILE"
  postmap "$TRANSPORT_FILE"
fi

# master.cf に pipe サービス追加
if ! grep -q "classifier unix" "$MASTER_CF"; then
  echo "classifier unix - n n - - pipe user=docker argv=/opt/venv/bin/python3 /opt/classifier/email_classifier.py \${recipient}" >> "$MASTER_CF"
fi

# main.cf に transport_maps 追加
if ! grep -q "transport_maps" "$MAIN_CF"; then
  echo "transport_maps = hash:/etc/postfix/transport" >> "$MAIN_CF"
fi

postmap /etc/postfix/transport

# postfix 再起動
postfix reload

## PythonとGeminiAPI環境
apt-get update
apt-get install -y python3.11 python3.11-venv python3.11-distutils
python3 -m venv /opt/venv
source /opt/venv/bin/activate
pip3 install google-cloud-aiplatform requests

echo "Default user-patches.sh successfully executed"

docker compose down && docker compose up -d
docker logs -f mailserver

From: billing@example.com
To: recipient@example.com
Subject: ご請求書の送付について

お世話になっております。

以下の通り、今月分のご請求書をお送りします。

----
請求書番号: INV-202505
金額: ¥123,456
期日: 2025年5月31日
----

何卒よろしくお願いいたします。

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