public string SendTriggerMail(string emailAddress,
                            string subscriberKey,
                            string triggerMailId)
{
    IExactTargetService exactTargetServiceClient = new ExactTargetServiceClient
            {
                ClientCredentials = { UserName = { UserName = "", Password = "" } }
            };

    var id = new ClientID { ID = 1234567, IDSpecified = true };
    var definition = new TriggeredSendDefinition
    {
        CustomerKey = triggerMailId,
        Client = id,
        FromAddress = "test@test.com",
        FromName = "Test",
        SendClassification = new SendClassification
        {
            SenderProfile = new SenderProfile
                        {
                            ReplyManagementRuleSet = new ReplyMailManagementConfiguration
                            {
                                EmailReplyAddress = "test@test.com",
                                EmailDisplayName = "Test",
                            }
                        }
        }
    };

    var send = new TriggeredSend { TriggeredSendDefinition = definition, Client = id };

    var subscriber = new Subscriber
    {
        EmailAddress = emailAddress,
        SubscriberKey = subscriberKey
    };

    var allAttributes = new List<Attribute>
                {
                    new Attribute { Name = "SomeAttribute", Value = "AttributeValue" }
                };

    subscriber.Attributes = allAttributes.ToArray();

    send.Subscribers = new[] { subscriber };
    APIObject[] sends = { send };

    var response = exactTargetServiceClient.Create(
        new CreateRequest(new CreateOptions(), sends));

    return response.OverallStatus;
}