Unable to resolve host name.

Ok, I have tried everything.. SmartFTP is allowed on my firewall and it still will not allow me to connect. This is what comes up:
[18:48:29] SmartFTP v3.0.1016.16
[18:48:29] Resolving host name "ftp.graingerspub.com"
[18:48:44] Unable to resolve host name.
[18:48:44] Active Help: https://www.smartftp.com/support/kb/81
[18:48:44] Connect failed. Waiting to retry (30s)...
[18:49:15] Connection attempt 2...
[18:49:15] Resolving host name "ftp.graingerspub.com"
[18:49:30] Unable to resolve host name.
[18:49:30] Active Help: https://www.smartftp.com/support/kb/81
[18:49:30] Connect failed. Waiting to retry (30s)...
[18:50:00] Connection attempt 3...
[18:50:00] Resolving host name "ftp.graingerspub.com"
[18:50:15] Unable to resolve host name.
[18:50:15] Active Help: https://www.smartftp.com/support/kb/81
[18:50:15] Connect failed. Waiting to retry (30s)...



And so on and so on.. It worked fine when i first installed the new version but then it just stopped.. Help?

There is a problem with the DNS server. We have answered your question by email.