Telnet is used to test open ports or administer remote servers via the command prompt.
The telnet command will need to be run from a Command prompt or terminal depending on your operating system (Windows, Mac or Linux)
Windows:
Telnet is not enabled by default, use the following steps to ensure it's enabled.
Start > search and click on Control Panel > Programs and Features > Turn Windows features on or off > Tick Telnet Client > Click OK
Once the feature has been added continue with the test.
Use your keyboard shortcuts, press and hold Windows button + R simultaneously and type "cmd" (without the quotes), alternatively simply click on the Start button and typing "cmd" would suffice.
Enter the following command at the prompt:
telnet <domain/server> <port> then hit enter, where <domain/server> is the hostname or IP address of the server.
eg: telnet mail.domain.tld 110
type quit to close session
Mac:
Open Terminal by navigating to /Applications/Utilities.
In the Terminal window type telnet followed by the <domain/server> <port>,
eg: telnet mail.domain.tld 110
type quit to close session
Linux
Press CTRL+Alt+T simulaneously
Type in telnet followed by the <domain/server> <port>
eg: telnet mail.domain.tld 110
type quit to close session
If you cannot connect, you may see one of the following messages, some other message, or no response:
- Tcp connect failed
- Connection refused
- Operation timed out
- Unable to connect to remote host
The exact verbiage you get back will be determined by your host.
A successful connection will rule out connectivity issues at the server, the next step in your investigation would be your ISP or your Mail Client.
