I have installed ISPConfig on ubuntu with all default settings using auto installer. After configuration, I have followed this url to configure SSL on all main services. From begenning, I am getting some errors in the mail servers like 10025 port being used by another process, 10026 is being used by another etc. I have restarted the whole server and then I got mail server running. But, later I got 10024 is being used by another process while sending mails. Below are the error logs from mail server section. connect to 127.0.0.1[127.0.0.1]:10024: Connection refused postfix/master: fatal: bind 127.0.0.1 port 10025: Address already in use postfix/master: fatal: bind 127.0.0.1 port 10026: Address already in use Can't connect to TCP port 10025 on 127.0.0.1 [Address already in use]#012 at line 64 in file /usr/share/perl5/Net/Server/Proto/TCP.pm Can anyone help me out how can I get my mail server working perfectly? I do not use SMTP from my server. I just use wordpress plugins to send mails from other SMTP servers and receive mails on my server. MX record is perfectly configured (It was working fine with CWP previously. I switched to ISP config to solve FTP error of CWP) Update: I am using ISPConfig 3.1.13 running on Ubuntu LTS 18.04. I can't even send mails from local server to local. I tried to find which process is using port 10025 and found that perl was using it. After reboot server, I got problem to port 10024 which was used by some other process. Sendmail is not installed on the server. Tried by restarting postfix server etc. Problem remains same.