Lookst like firewalld is not opening port 25. I tried adding the smtp service, and port 25 separately as well, yet, I am unable to telnet to the server. Any tips?
[root@host ~]# firewall-cmd --zone=public --list-all public (default, active) interfaces: eth0 sources: services: dhcpv6-client http https smtp ssh ports: 3762/tcp 25/tcp 7683/tcp 4424/tcp masquerade: no forward-ports: icmp-blocks: rich rules: [root@host ~]# nmap XXXXXXXMYIP Starting Nmap 6.40 ( http://nmap.org ) at 2016-01-14 00:11 CET Nmap scan report for CentOS-72-64-minimal (XXXMYIP) Host is up (0.0000080s latency). Not shown: 990 closed ports PORT STATE SERVICE 21/tcp open ftp 53/tcp open domain 80/tcp open http 110/tcp open pop3 143/tcp open imap 443/tcp open https 993/tcp open imaps 995/tcp open pop3s 3306/tcp open mysql 20000/tcp open dnp Nmap done: 1 IP address (1 host up) scanned in 0.05 seconds [root@host ~]#