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TCP Connect

What you see when your domain has this problem
Unable to Connect Details area Ignore

More Information About Tcp Connect

The requested TCP address could not be reached.

Additional Information

When the TCP address is checked by our servers, we wait a standard 15 seconds for a response. If we do not detect a response, this error will be triggered.

TCP (Transmission Control Protocol) is a specific way to transmit and format data over a network between two IP addresses, hence TCP/IP. Most web traffic uses the TCP protocol, including email and other protocols, such as HTTP, HTTPS, SMTP, POP3, IMAP, SSH, and FTP.

If a TCP hostname is requested (e.g., the request goes out to a DNS server and gets converted into an IP address.


  • Double check the TCP address, including the port, if set
  • If using a hostname, try running a DNS Lookup on your domain to see if there are any issues with your DNS servers.
  • If you are a paid member of MxToolbox, you can view the history and performance data of a monitor you’ve set up to pinpoint when this problem started occurring.
  • One of the best ways to get help if you are a MxToolbox paid member is to create a support ticket, and one of our staff will be happy to assist you.