what is the cause of error: "No such host is known"

Question

Hi,
I get the following error intermittently when replying to emails with mail.dll
I would just like to understand is the host in question here my own mailserver to which i am somehow losing connectivity to? or is it the domain of the email that I am trying to reply to?

Limilabs.Client.ServerException: No such host is known ---> System.Net.Sockets.SocketException: No such host is known
at System.Net.Dns.GetAddrInfo(String name)
at System.Net.Dns.InternalGetHostByName(String hostName, Boolean includeIPv6)
at System.Net.Dns.GetHostAddresses(String hostNameOrAddress)
at System.Net.Sockets.Socket.Connect(String host, Int32 port)
at Limilabs.Client.ClientBase.Connect(String host, Int32 port, Boolean useSSL)
--- End of inner exception stack trace ---
at Limilabs.Client.ClientBase.Connect(String host, Int32 port, Boolean useSSL)
at Limilabs.Client.SMTP.Smtp.Connect(String host)

Answer 1

It is about your mail server, but it's not the server that is not accessible.

It's the DNS server that respond that the address you are using doesn't exist and can't be translated to IP address.