Comments on How to Install an Email Server with ISPConfig on Debian 10

Testing if port 25 is open

Testing from home computer may not work, since ISP usually blocks port 25 for home users and is not willing to make exceptions. Business connections may get port 25 opened if they ask for it.

There are web tools that check if a port is open, but they only check the computer you are sitting at, not arbitrary other IP-addresses. So you can check your home computer or rather home Internet connection for open ports with for example yougetsignal.com/open-ports/.

From you e-mail server host, you can check outgoing port 25 by installing netcat and then trying to connect to some computer where you know port 25 is open. Another e-mail server is a good target.

$ nc -zv mail.google.com 25

For testing incoming port 25, you would need another computer where port 25 is open, and then target the netcat test to your e-mail host.

I followed this to the latter, but still, no email sent or received!!!

@martin: This can have many reasons, e.g. when your isp or datacenter blocks port 25, nd sof the mail domain is not setup correctly or you might have made a mistake while editing postfix config files. Make a post in the ispconfig forum here at howtoforge which includes an excerpt of your mail.log file.

There is a typo in the commands example in chapter "Installing OS". LIne breaks got lost somehow. It should be

root@posti:~# hostname

posti

root@posti:~# hostname -f

posti.taleman.ovh

root@posti:~#