Telnet allows you to see if you have а connection to a specific hostname on a given port. To use Telnet you need to execute the following command through your computer’s console or command prompt:
telnet HOSTNAME PORT

To quit telnet use the combination of “Ctrl” and closing square bracket “]”, after that type “quit” and press enter.

You need to replace HOSTNAME with the hostname/website that you are having issues with. The PORT needs to be replaced with a port number depending on the service you are going to test:
Port 21 – used for FTP;
Port 25 and port 587 – used for SMTP, SMTP+TLS, and SMTP+SSL;
Port 80 – used for HTTP;
Port 443 – used for HTTPS;
Port 110 – used for POP3 and POP3+TLS;
Port 143 – used for IMAP and IMAP+TLS;
Port 993 – used for IMAP+SSL;
Port 995 – used for POP3+SSL;
Port 2222 – used for SSH.

So for example if you experience problems with HTTPS access on a domain named yourdomain.com, you need to execute the following command:
telnet yourdomain.com 443

For some Widows versions you need to explicitly enable Telnet, you can find out how to do this using the official tutorial from the Microsoft Wiki -> http://social.technet.microsoft.com/wiki/contents/articles/910.windows-7-enabling-telnet-client.aspx)

If you connect successfully you should receive either a blank screen or server response stating the name of the service.

If you cannot connect to our servers, you should receive an error like:
telnet: could not resolve HOSTNAME/PORT: Name or service not known
In the latter case, please try using Telnet for another port on our servers as this will help you to determine whether our firewall is blocking your IP address or the problem lies elsewhere. If you cannot connect through another port, please open a Trouble Ticket concerning the problem from your Hosting Control Panel -> Support -> Support Center -> Trouble Tickets, so our Support team can investigate the issue and check if we are blocking your IP address for some reason. If you can connect through another port, this means we are not blocking your IP address and something is restricting the connection. Few things that could be blocking the connection are – firewall of your local computer, anti-virus software of your local computer, local router and your ISP.

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