Meaning of TELNET and TRACEROUTE commands

This guide presents commands that can be executed to test a connection or a network in order to further specify the possible source of error.

Performing a Telnet

TELNET allows testing the connection to a server without taking into account all the additional settings of a mail client or an FTP client in order to determine the origin of a problem. If the connection fails on an SMTP server, you may need to check if your firewall is blocking port 587 or 465, for example.

on macOS

1. search for Network Utility
2. go to the Ping, Lookup, or Traceroute tab depending on what you want to test
3. you can also use Terminal and in the window that opens, depending on what you want to test, type:
   traceroute [server]
nc [server] [port]
   Replace [server] with the server name or its IP address, same for [port]

on Windows

Activate Telnet beforehand if necessary.

1. open Run and type 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 (tests the SMTP port if your email software does not allow sending emails)

on Android

1. use the free Simple Telnet Client application, which allows very simple testing via 2 fields to fill in (e.g., mail.infomaniak.com and port 143 or 993).

Performing a PING

PING allows knowing if a machine is accessible over the Internet. You can also check with this tool if you are addressing the correct machine, for example during a DNS change, by looking at the obtained IP address. It is possible to ping a domain name, a hostname, or an IP address.