Postfix (Email) - Resolve "Could not open connection to host, on port 25: Connect failed"

In this example, this error appears when attempting to connect to a Postfix email server from a Windows machine in the LAN using a command line prompt. Following are things to check:

  1. Ensure you can ping and tracert from the Windows machine to the email server
  2. Ensure port 25 is open on the email server. This can be done using Nmap. If port 25 is not open:
    • Open port 25 in iptables on the email server
    • Use the /sbin/service postfix status command to ensure the Postfix email service is running
  3. Ensure the /etc/postfix/ file has inet_interfaces set to "all"


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