Use PHP sendmail from Docker container to send through host Postfix

I'm not sure about using the host's config/postfix however I can suggest an alternative solution that may work just as well. Add a postfix container and copy the configs from the host to the container:

services:  application:    image: some-company/some-application    environment:      - APPLICATION_ENV    ports:      - 80:80  smtp:    image: namshi/smtp    environment:      - MAILNAME      - SMARTHOST_USER      - SMARTHOST_PASSWORD    volumes:      - /etc/postfix/main.cf:/etc/postfix/main.cf    ports:      - 25:25

Then you can use smtp as your mailer host / transport and the user/pass from the environment.

I am not a container expert, but if I understood correctly, you are trying to acccess 127.0.0.1 within the container (php.ini localhost config resolves to 127.0.0.1), and I assume that is not the hosts address, it points to the container internals.

Figure out the host IP and change in the php.ini:

[mail function]SMTP = host_addresssmtp_port = 25

The best solution which I have found is to install msmtp and add the following to the php.ini

sendmail_path = /usr/bin/msmtp -t  --host host.docker.internal --from php@docker

Now your mail will be received by your mail server (smpt4dev or mailh