Connect Method (Smtp)

Connect to an SMTP server using Session parameters. Any existing connection is aborted.

Syntax

Visual Basic (Declaration)
Visual Basic (Usage)
C#
Managed Extensions for C++
C++/CLI

Public Sub Connect()

Dim instance As Smtp
 
instance.Connect()

public void Connect()

public: void Connect();

public:
void Connect();

Remarks

SSL encryption is negotiated if Session.Security.Encrypt == Encrypt.Implicit.

Smtp.Capabilities is populated after connecting.

If Session.RemoteEndPoint.Port is 0, the default port for the current Session configuration will be used.

Authenticate is normally used after this method. If not, it is up to the application to send any necessary authentication commands to the server.

Example

This example demonstrates connecting to an Smtp server, with options for encryption (Explicit/Implicit), and authenticating the user.

using System.Security.Cryptography.X509Certificates;
using System.Security.Authentication;
using System.Net.Security;

/// <summary>
/// Connects to an Smtp server, optionally using encryption (Explicit/Implicit), and authenticates the user.
/// </summary>
/// <param name="mySmtp">The Smtp instance to connect and authenticate</param>
/// <param name="hostNameOrAddress">The server's hostname or IP address</param>
/// <param name="auth">Authentication method to use. 'Auto' is suitable for most circumstances.</param>
/// <param name="username">Username</param>
/// <param name="password">Password</param>
/// <param name="encryption">Controls whether SSL/TLS is used, and the implementation. None/Explicit/Implicit.</param>
private void ConnectAndAuthenticate(Smtp mySmtp, string hostNameOrAddress, Authentication auth, string username, string password, Encrypt encryption)
{
    if (encryption != Encrypt.None)
    {
        //Set the method of encryption - Implicit/Explicit
        mySmtp.Session.Security.Encrypt = encryption;

        //Optionally set the protocols available for SSL/TLS negotiation (defaults to SslProtocols.Default)
        //TLS 1.1/1.2 requires .NET 4.5+. See the SslProtocols MSDN documentation for more information.
        mySmtp.Session.Security.Protocols = SslProtocols.Tls | SslProtocols.Ssl3;

        //Specify the server certificate validation callback
        mySmtp.Session.Security.ValidationCallback = remoteCertificateValidation;
    }

    //Set the server address and port. If the server uses a non-standard port, it should be substituted here.
    //GetDefaultPort() returns the common port used for the security configuration.
    mySmtp.Session.RemoteEndPoint = new IPEndPoint(hostNameOrAddress, Pop.GetDefaultPort(mySmtp.Session));

    //Connect to the server.
    mySmtp.Connect();

    //Authenticate the user.
    mySmtp.Session.Username = username;
    mySmtp.Session.Password = password;
    mySmtp.Session.Authentication = auth;
    mySmtp.Authenticate();
}

private bool remoteCertificateValidation(Object sender, X509Certificate remoteCertificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
{
    //For this simple snippet, accept all server certificates. Please see the 'Security' top-level help topics, or 
    //the System.Net.Security.RemoteCertificateValidationCallback MSDN documentation, for more information.
    return true;
}

Visual Basic

Imports System.Security.Cryptography.X509Certificates
Imports System.Security.Authentication
Imports System.Net.Security

''' <summary>
''' Connects to an Smtp server, optionally using encryption (Explicit/Implicit), and authenticates the user.
''' </summary>
''' <param name="mySmtp">The Smtp instance to connect and authenticate</param>
''' <param name="hostNameOrAddress">The server's hostname or IP address</param>
''' <param name="auth">Authentication method to use. 'Auto' is suitable for most circumstances.</param>
''' <param name="username">Username</param>
''' <param name="password">Password</param>
''' <param name="encryption">Controls whether SSL/TLS is used, and the implementation. None/Explicit/Implicit.</param>
Private Sub ConnectAndAuthenticate(ByVal mySmtp As Smtp, ByVal hostNameOrAddress As String, ByVal auth As Authentication, ByVal username As String, ByVal password As String, ByVal encryption As Encrypt)
    If encryption <> Encrypt.None Then
        'Set the method of encryption - Implicit/Explicit
        mySmtp.Session.Security.Encrypt = encryption

        'Optionally set the protocols available for SSL/TLS negotiation (defaults to SslProtocols.Default)
        'TLS 1.1/1.2 requires .NET 4.5+. See the SslProtocols MSDN documentation for more information.
        mySmtp.Session.Security.Protocols = SslProtocols.Tls Or SslProtocols.Ssl3

        'Specify the server certificate validation callback
        mySmtp.Session.Security.ValidationCallback = AddressOf remoteCertificateValidation
    End If

    'Set the server address and port. If the server uses a non-standard port, it should be substituted here.
    'GetDefaultPort() returns the common port used for the security configuration.
    mySmtp.Session.RemoteEndPoint = New IPEndPoint(hostNameOrAddress, Pop.GetDefaultPort(mySmtp.Session))

    'Connect to the server.
    mySmtp.Connect()

    'Authenticate the user.
    mySmtp.Session.Username = username
    mySmtp.Session.Password = password
    mySmtp.Session.Authentication = auth
    mySmtp.Authenticate()
End Sub

Private Function remoteCertificateValidation(ByVal sender As Object, ByVal remoteCertificate As X509Certificate, ByVal chain As X509Chain, ByVal sslPolicyErrors As SslPolicyErrors) As Boolean
    'For this simple snippet, accept all server certificates. Please see the 'Security' top-level help topics, or 
    'the System.Net.Security.RemoteCertificateValidationCallback MSDN documentation, for more information.
    Return True
End Function

Reference

Smtp Class
Smtp Members