Use PHP mail() function in docker installation with mailcatcher

Question

I have set up a local development environment using docker compose. It consists of nginx, php-fpm, mariadb, and mailcatcher. Everything is working good, but I can't make the mail() function work.

This is my compose.yaml

version: '3.8'

services:
  nginx:
    image: nginx:latest
    ports:
      - "80:80"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf
      - ./html:/var/www/html
    networks:
      - internal
    depends_on:
      - php    

  php:
    build:
      context: .
      dockerfile: ./php/Dockerfile
    volumes:
      - ./html:/var/www/html
      - ./custom-php.ini:/usr/local/etc/php/conf.d/custom-php.ini
    environment:
      PHP_INI_SCAN_DIR: /usr/local/etc/php/conf.d      
    networks:
      - internal    

  mariadb:
    image: mariadb:10.4    
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: dbname
      MYSQL_USER: dbuser
      MYSQL_PASSWORD: dbpassword
    ports:
      - "3306:3306"
    volumes:
      - mariadb_jazdy_data:/var/lib/mysql
    networks:
      - internal

  mailcatcher:
    image: sj26/mailcatcher
    ports:
      - "1080:1080"
      - "1025:1025"    

networks:
  internal:

volumes:
  mariadb_jazdy_data:

This is my Dockerfile

FROM php:7.4-fpm
RUN curl -sSLf \
        -o /usr/local/bin/install-php-extensions \
        https://github.com/mlocati/docker-php-extension-installer/releases/latest/download/install-php-extensions && \
    chmod +x /usr/local/bin/install-php-extensions && \
    install-php-extensions mysqli

and this is my custom-php.ini

; Enable mysqli extension
extension=mysqli.so

[mail function]
SMTP=127.0.0.1
smtp_port=1025
sendmail_from=sender@example.com

I tried different configuration for the SMTP, including localhost, or mailcatcher. Without any success.

What am I missing here? I really would like to make this work as I literally spent hours of googling and asking chat gpt. Thanks.

I tried using different docker images, installing sendmail in Dockerfile (https://r.je/sendmail-php-docker), but nothing seems to be working.

Answer 1

I'm gonna answer my own question with the correct solution where Alex Howansky led me to.

However, I've made some changes also to the original compose.yaml, where I forgot to add the network directive under mailcatcher. But later, I found out, it didn't have to be there, at all.

So these is the final configuration how I made it work.

compose.yaml

version: '3.8'

services:
  nginx:
    image: nginx:latest
    ports:
      - "80:80"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf
      - ./html:/var/www/html    
    depends_on:
      - php    

  php:
    build:
      context: .
      dockerfile: ./php/Dockerfile
    volumes:
      - ./html:/var/www/html
      - ./custom-php.ini:/usr/local/etc/php/conf.d/custom-php.ini
    environment:
      PHP_INI_SCAN_DIR: /usr/local/etc/php/conf.d          

  mariadb:
    image: mariadb:10.4    
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: dbname
      MYSQL_USER: dbuser
      MYSQL_PASSWORD: dbpassword
    ports:
      - "3306:3306"
    volumes:
      - mariadb_jazdy_data:/var/lib/mysql    

  mailcatcher:
    image: sj26/mailcatcher
    ports:
      - "1080:1080"          

volumes:
  mariadb_jazdy_data:

Dockerfile

FROM php:7.4-fpm
RUN apt-get update && apt-get install -y build-essential software-properties-common
RUN apt-get install -y libsqlite3-dev ruby-dev
RUN gem install mailcatcher
RUN curl -sSLf \
        -o /usr/local/bin/install-php-extensions \
        https://github.com/mlocati/docker-php-extension-installer/releases/latest/download/install-php-extensions && \
    chmod +x /usr/local/bin/install-php-extensions && \
    install-php-extensions mysqli
RUN mv "$PHP_INI_DIR/php.ini-production" "$PHP_INI_DIR/php.ini"

custom-ini.php

; Enable mysqli extension
extension=mysqli.so

[mail function]
sendmail_path=/usr/bin/env catchmail --smtp-ip mailcatcher --smtp-port 1025