This documentation is archived and is not being maintained.

SmtpClient.Credentials Property

Note: This property is new in the .NET Framework version 2.0.

Gets or sets the credentials used to authenticate the sender.

Namespace: System.Net.Mail
Assembly: System (in system.dll)

public ICredentialsByHost Credentials { get; set; }
/** @property */
public ICredentialsByHost get_Credentials ()

/** @property */
public void set_Credentials (ICredentialsByHost value)

public function get Credentials () : ICredentialsByHost

public function set Credentials (value : ICredentialsByHost)

Property Value

An ICredentialsByHost that represents the credentials to use for authentication; or a null reference (Nothing in Visual Basic) if no credentials have been specified.

Exception typeCondition


You cannot change the value of this property when an email is being sent.

Some SMTP servers require that the client be authenticated before the server will send e-mail on its behalf. To use your default network credentials, you can set the UseDefaultCredentials to true instead of setting this property.

Credentials information can also be specified using the application and machine configuration files. For more information, see mailSettings Element (Network Settings). If information is specified using the Credentials property, this information overrides the configuration file settings.

Caution noteCaution

If you provide credentials for basic authentication, they are sent to the server in clear text. This can present a security issue because your credentials can be seen, and then used by others.

The following code example demonstrates setting the credentials used to send an e-mail.

public static void CreateTestMessage1(string server, int port)
    string to = "";
    string from = "";
    string subject = "Using the new SMTP client.";
    string body = @"Using this new feature, you can send an e-mail message from an application very easily.";
    MailMessage message = new MailMessage(from, to, subject, body);
    SmtpClient client = new SmtpClient(server, port);
    // Credentials are necessary if the server requires the client 
    // to authenticate before it will send e-mail on the client's behalf.
    client.Credentials = CredentialCache.DefaultNetworkCredentials;


Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0