apt -y ubstall thunderbird 3대 서버 웹서버 도메인 : ibj.kr netstat -ant | grep 80 netstat -ant | grep 21 netstat -ant | grep 53 netstat -ant | grep 25 netstat -ant | grep 110 netstat -ant | grep 143 sendmail : 메일 보내기 sudo apt -y install dovecot imapd sudo apt -y install dovecot-pop3d