How to add mail service to the Bookstack container

MAIL_DRIVER=smtp
MAIL_FROM_NAME="BookStack"
[email protected]
MAIL_HOST=localhost
MAIL_PORT=587
MAIL_USERNAME=null
MAIL_PASSWORD=null
MAIL_ENCRYPTION=null

---
version: "2"
services:
  bookstack:
    image: lscr.io/linuxserver/bookstack
    container_name: bookstack
    environment:
      - PUID=1000
      - PGID=1000
      - APP_URL=
      - DB_HOST=bookstack_db
      - DB_PORT=3306
      - DB_USER=bookstack
      - DB_PASS=Admin@123
      - DB_DATABASE=bookstackapp
      - MAIL_DRIVER=smtp
      - MAIL_FROM_NAME=Bookstack
      - [email protected]
      - MAIL_HOST=smtp.gmail.com
      - MAIL_PORT=587
      - [email protected]
      - MAIL_PASSWORD=your_mail_app_password
      - MAIL_ENCRYPTION=null
    volumes:
      - ./bookstack_app_data:/config
    ports:
      - 6875:80
    restart: unless-stopped
    depends_on:
      - bookstack_db
  bookstack_db:
    image: lscr.io/linuxserver/mariadb
    container_name: bookstack_db
    environment:
      - PUID=1000
      - PGID=1000
      - MYSQL_ROOT_PASSWORD=Admin@123
      - TZ=Europe/London
      - MYSQL_DATABASE=bookstackapp
      - MYSQL_USER=bookstack
      - MYSQL_PASSWORD=Admin@123
    volumes:
      - ./bookstack_db_data:/config
    restart: unless-stopped

docker run -d \
  --name=bookstack \
  -e PUID=1000 \
  -e PGID=1000 \
  -e TZ=Etc/UTC \
  -e APP_URL=<yourbaseurl> \
  -e DB_HOST=<yourdbhost> \
  -e DB_PORT=<yourdbport> \
  -e DB_USER=<yourdbuser> \
  -e DB_PASS=<yourdbpass> \
  -e DB_DATABASE=bookstackapp \
  -e MAIL_DRIVER=smtp \
  -e MAIL_FROM_NAME="BookStack" \
  -e [email protected] \
  -e MAIL_HOST=localhost \
  -e MAIL_PORT=587 \
  -e MAIL_USERNAME=null \
  -e MAIL_PASSWORD=null \
  -e MAIL_ENCRYPTION=null \
  -p 6875:80 \
  -v /path/to/data:/config \
  --restart unless-stopped \
  lscr.io/linuxserver/bookstack:latest