Too simple to making a mailing list in postfix, just define a mailing list name and recipients in /etc/postfix/virtual, like this: dev-group dev1@company.com dev2@company.com dev3@company.com, after that, generate the virtual db by postmap /etc/postfix/virtual.

Don’t forget add virtual_alias_maps=hash:/etc/postfix/virtual in your main.cf file, and restart postfix finally.

I think I need study postfix systemally, just build a private smtp/imap server.