Rebex SMTP

SMTP, MIME, S/MIME libraries for .NET

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Proxies and custom sockets

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SOCKS4/SOCKS5 proxy servers 

To connect through SOCKET4, SOCKET4a or SOCKS5 proxy servers, set Smtp.Proxy properties before calling the Connect method. Use ProxyType property to specify the proxy type: 

// create client instance
// ...

// use SOCKS5 proxy
client.Proxy.ProxyType = ProxyType.Socks5;
client.Proxy.Host = proxyHost;
client.Proxy.Port = proxyPort;
client.Proxy.UserName = proxyUserName;

// connect to the server
client.Connect(hostname);

' create client instance
' ...

' use SOCKS5 proxy
client.Proxy.ProxyType = ProxyType.Socks5
client.Proxy.Host = proxyHost
client.Proxy.Port = proxyPort
client.Proxy.UserName = proxyUserName

' connect to the server
client.Connect(hostname)

HTTP CONNECT proxy servers 

To connect through a HTTP proxy server, set Smtp.Proxy or Smtp.Proxy properties before calling the Connect method. Make sure the proxy server supports HTTP CONNECT method, and set the ProxyType property to HttpConnect: 

// create client instance (Rebex.Net.Smtp/Imap/Pop3/Ews)
// ...

// use HTTP CONNECT proxy
client.Proxy.ProxyType = ProxyType.HttpConnect;
client.Proxy.Host = proxyHost;
client.Proxy.Port = proxyPort;
client.Proxy.UserName = proxyUserName;
client.Proxy.Password = proxyPassword;

// connect to the server
client.Connect(hostname);

' create client instance
' ...

' use HTTP CONNECT proxy
client.Proxy.ProxyType = ProxyType.HttpConnect
client.Proxy.Host = proxyHost
client.Proxy.Port = proxyPort
client.Proxy.UserName = proxyUserName
client.Proxy.Password = proxyPassword

' connect to the server
client.Connect(hostname)

Proxies with single sign-on 

Some HTTP CONNECT proxies support NTLM authentication with single sign-on. To take advantage of this feature, set the AuthenticationMethod property to ProxyAuthentication.Ntlm. 

// create client instance (Rebex.Net.Smtp/Imap/Pop3/Ews)
// ...

// use HTTP CONNECT proxy
client.Proxy.ProxyType = ProxyType.HttpConnect;
client.Proxy.Host = proxyHost;
client.Proxy.Port = proxyPort;

// use single sign-on
client.Proxy.AuthenticationMethod = ProxyAuthentication.Ntlm;

// connect to the server
client.Connect(hostname);

' create client instance
' ...

' use HTTP CONNECT proxy
client.Proxy.ProxyType = ProxyType.HttpConnect
client.Proxy.Host = proxyHost
client.Proxy.Port = proxyPort

' use single sign-on
client.Proxy.AuthenticationMethod = ProxyAuthentication.Ntlm

' connect to the server
client.Connect(hostname)
Learn how to use single sign-on to authenticate to an mail server.

SSH server as proxy 

It's possible to tunnel SMTP or Rebex SMTP sessions through an SSH server, essentially using it as a proxy server. See SSH Tunneling for more information and sample code.

Custom transport layer - ISocket 

Rebex libraries make it possible to implement a custom transport layer, giving you full control over the network communication. All you need to do is implement a custom ISocketFactory and ISocket interfaces and instruct the Smtp or Smtp object to use them. 

// create client instance (Rebex.Net.Smtp/Imap/Pop3/Ews)
// ...

// initialize factory
SimpleSocketFactory factory = new SimpleSocketFactory();
factory.SocketConnecting += factory_SocketConnecting;

// use the factory
client.SetSocketFactory(factory);

// connect to the server
client.Connect(hostname);

' create client instance
' ...

' initialize factory
Dim factory As New SimpleSocketFactory()
AddHandler factory.SocketConnecting, AddressOf factory_SocketConnecting

' use the factory
client.SetSocketFactory(factory)

' connect to the server
client.Connect(hostname)

Custom transport layer (ISocket/ISocketFactory) implementation

/// <summary>
/// Exposes SocketConnected event which is raised
/// when a socket successfully connects to a remote end.
/// </summary>
public class SimpleSocketFactory : ISocketFactory
{
    /// <summary>
    /// Occurs when a socket successfully connects to a remote end.
    /// </summary>
    public event EventHandler SocketConnecting;

    // creates custom ISocket implementation
    ISocket ISocketFactory.CreateSocket()
    {
        return new SimpleSocket(this);
    }

    // raises event
    private void OnSocketConnecting()
    {
        EventHandler h = SocketConnecting;
        if (h != null)
            h(this, EventArgs.Empty);
    }

    // simple ISocket implementation
    // (core functionality is taken from ProxySocket)
    private class SimpleSocket : ProxySocket, ISocket
    {
        // creator object
        private readonly SimpleSocketFactory _factory;

        public SimpleSocket(SimpleSocketFactory factory)
        {
            _factory = factory;
        }

        // connects to a server and raises SocketConnected event
        void ISocket.Connect(string serverName, int serverPort)
        {
            _factory.OnSocketConnecting();
            base.Connect(serverName, serverPort);
        }

        // connects to a server and raises SocketConnected event
        void ISocket.Connect(EndPoint endpoint)
        {
            _factory.OnSocketConnecting();
            base.Connect(endpoint);
        }
    }
}

''' <summary>
''' Exposes SocketConnected event which is raised
''' when a socket successfully connects to a remote end.
''' </summary>
Public Class SimpleSocketFactory
    Implements ISocketFactory
    ''' <summary>
    ''' Occurs when a socket successfully connects to a remote end.
    ''' </summary>
    Public Event SocketConnecting As EventHandler

    ' creates custom ISocket implementation
    Private Function ISocketFactory_CreateSocket() As ISocket Implements ISocketFactory.CreateSocket
        Return New SimpleSocket(Me)
    End Function

    ' raises event
    Private Sub OnSocketConnecting()
        RaiseEvent SocketConnecting(Me, EventArgs.Empty)
    End Sub

    ' simple ISocket implementation
    ' (core functionality is taken from ProxySocket)
    Private Class SimpleSocket
        Inherits ProxySocket
        Implements ISocket
        ' creator object
        Private ReadOnly _factory As SimpleSocketFactory

        Public Sub New(factory As SimpleSocketFactory)
            _factory = factory
        End Sub

        ' connects to a server and raises SocketConnected event
        Private Sub ISocket_Connect(serverName As String, serverPort As Integer) Implements ISocket.Connect
            _factory.OnSocketConnecting()
            MyBase.Connect(serverName, serverPort)
        End Sub

        ' connects to a server and raises SocketConnected event
        Private Sub ISocket_Connect(endpoint As EndPoint) Implements ISocket.Connect
            _factory.OnSocketConnecting()
            MyBase.Connect(endpoint)
        End Sub

    End Class
End Class

Please note that custom communication layer and proxy support are mutually exclusive - it's not possible to use both at the same time.

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