Perform a TELNET / TRACEROUTE command

This guide presents commands that can be executed to test a connection or a network and thus further specify the potential source of error.

Perform a Telnet…

TELNET allows you to test the connection to a server without considering all the additional settings of a mail or FTP application in order to determine the source of a problem. If the connection does not go through on an SMTP server, for example, you will need to check if your firewall is not blocking port 587 or 465.

… on macOS

1. Look for Network Utility.
2. Go to the Ping, Lookup or Traceroute tab depending on what you want to test.
3. You can also use a terminal application (command line interface, CLI) on your device and, depending on what you want to test, enter:
   traceroute [server] 
nc [server] [port] 
   Replace [server] with the server name or its IP address, same for [port]…

… on Windows

Enable Telnet in advance if necessary.

1. Use a command-line interface (CLI) application like Terminal on your device, for example by typing Run then cmd.
2. In the window that opens, depending on what you want to test, type:
   tracert [server] 
telnet [server] [port] 
   Example: telnet mail.infomaniak.com 587 (allows you to test the SMTP port if your software/email client does not allow sending emails)…

… on Android

1. Use the application Simple Telnet Client which allows you to test very simply via 2 fields to fill in (for example mail.infomaniak.com and the port 143 or 993)…

Perform a PING

PING allows you to check if a machine is accessible via the Internet. You can also use this tool to ensure you are addressing the correct machine, for example during a DNS change, by checking the IP address obtained. It is possible to perform a ping on a domain name, a hostname or an IP address.