I had gitlab installed on a server with plesk and there were mails working without doing something special. Now I have installed gitlab on a new server with ISPConfig and I have gitlab running with this docker image: gitlab/gitlab-ce:latest. I'm using apache reverse proxy to access gitlab in the browser. How must I configure ISPConfig and gitlab that E-Mails are working? I have created a new gitlab user and the E-Mail to reset the password does not been send.