We're running TFS for our source control and TeamCity for our build server running on Windows 2008.

Everything was working fine, but I believe some network issues occurred, and now our TeamCity build agent can't access TFS. It is getting the following proxy error:

ERROR - The proxy name could not be resolved: '[a proxy server name]'

Some more details:

  • Not sure where the proxy server is coming from. I can't ping it, and it doesn't seem that other users are getting routed through it
  • When I log remote into the box, I can access the TFS server from my session, so it seems that it's using different proxy settings for me than the TeamCity process.
  • If I change the Team City services to run under my network account, they still get the same proxy error message.
  • I believe it should be an intranet connection. They are accessing each other through a FQDN of MachineName.SubDomain.Domain.com, where subdomain and domain are the same.
  • The services are running under Local System. We do not have a dedicated NT account for them to run under, and this was all working fine for months.

Is there some setting that controls whether services go through a proxy for intranet access? I don't think I can log in as Local System directly and start mucking with the IE proxy settings.



Check user account that you use to run TeamCity windows service. Also check if Team Explorer is able to connect to TFS from the user account you use to run TeamCity server.

  • Thanks for the tip. Ran into a similar issue where TeamCity could not connect to our TFS server because the host name could not be resolved. It turns out that the account under which TeamCity was running had lost permissions to c:\windows\syswow64\dnsapi.dll so it couldn't make DNS lookups even though my own user account did not have a problem. Logging in as the service account helped pinpoint the problem. – Holistic Developer Jun 14 '16 at 1:58

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