ImapFolder Class

public class ImapFolder : MailFolder, IImapFolder, 
	IMailFolder, IEnumerable<MimeMessage>, IEnumerable

public static void DownloadMessages ()
{
    using (var client = new ImapClient ()) {
        client.Connect ("imap.gmail.com", 993, SecureSocketOptions.SslOnConnect);

        client.Authenticate ("username", "password");

        client.Inbox.Open (FolderAccess.ReadOnly);

        var uids = client.Inbox.Search (SearchQuery.All);

        foreach (var uid in uids) {
            var message = client.Inbox.GetMessage (uid);

            // write the message to a file
            message.WriteTo (string.Format ("{0}.eml", uid));
        }

        client.Disconnect (true);
    }
}