Hi,

My .NET 2005 application is on a server outsite company's domain. SQL server is in domain and port for sql server is open. TCP/IP is set for remote connection in SQL Server. Connection string in .config is

    <add name="X_Conn" connectionString="Data Source=XXX;Initial Catalog=XXX;User ID=XX; Password=XXX;" providerName="System.Data.SqlClient"/>

I receive the error below:

An error has occurred while establishing a connection to the server. When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)

thanks a lot in advance!

 Check the Remote connection properties.

Sql Server 2005 >>  Configuration Tools >> SQL Server Surface Area Configuration

Now open the  

Surface area config for services and connections

then Select your server. and check the Remote connection properties, 

Go to

Program--> Microsoft Sql server 2005 --> Sql server 2005 surdface area Configuration --> DataBase Engine --> Remote connection

Then Select Local and Remote  Connection

In its sub section select Using both TCP/IP and NamePipe

Make sure that SQL server is operating in Mixed Mode.  Refer to article below.

 http://www.vbsociety.com/Configure-Microsoft-SQL-Server-for-Mixed-Mode-Authentication.html

Siby