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CredentialCache.Add Method (String, Int32, String, NetworkCredential)

Adds a NetworkCredential instance for use with SMTP to the credential cache and associates it with a host computer, port, and authentication protocol. Credentials added using this method are valid for SMTP only. This method does not work for HTTP or FTP requests.

Namespace:  System.Net
Assemblies:   System (in System.dll)
  System.Net.Primitives (in System.Net.Primitives.dll)

public void Add(
	string host,
	int port,
	string authenticationType,
	NetworkCredential credential


Type: System.String

A String that identifies the host computer.

Type: System.Int32

A Int32 that specifies the port to connect to on host.

Type: System.String

A String that identifies the authentication scheme used when connecting to host using cred. See Remarks.

Type: System.Net.NetworkCredential

The NetworkCredential to add to the credential cache.


host is null.


authType is null.


authType not an accepted value. See Remarks.


port is less than zero.

This method places a NetworkCredential instance for use with SMTP into the CredentialCache. The cache stores credentials in the order in which they are added to it. When the GetCredential(String, Int32, String) method is called, it returns a NetworkCredential instance that is selected by matching the host, port, and authType. The comparison is done case-insensitively.

The supported values for authType are "NTLM", "Digest", "Kerberos", and "Negotiate".

Credentials added with this method are only valid for use with SMTP. This method does not work for HTTP or FTP protocols.

The following code example initializes a CredentialCache with multiple security credentials for use with SMTP and uses one of those credentials with a SmtpClient.

        SmtpClient client = new SmtpClient("ContosoMail", 45);
        MailAddress from = new MailAddress("sender@SenderMailServerName.com", "Sender Name");
        MailAddress to = new MailAddress("recepient@RecepientMailServerName.com", "Recepient Name");
        MailMessage message = new MailMessage(from, to);

        message.Body = "This is a test e-mail message sent by an application. ";
        message.Subject = "Test Email using Credentials";

        NetworkCredential myCreds = new NetworkCredential("username", "password", "domain");
        CredentialCache myCredentialCache = new CredentialCache();        
            myCredentialCache.Add("ContoscoMail", 35, "Basic", myCreds);
            myCredentialCache.Add("ContoscoMail", 45, "NTLM", myCreds);

            client.Credentials = myCredentialCache.GetCredential("ContosoMail", 45, "NTLM");
		    catch(Exception e)
			      Console.WriteLine("Exception is raised. ");
			      Console.WriteLine("Message: {0} ",e.Message);

.NET Framework

Supported in: 4.6, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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