I need Send approval mail use code .

We know in Exchange Server, We can open EMC set TransportRule , and set Transport Rule Action "ModerateMessageByUserAction" or  "ModerateMessageByManagerAction".

I need curstom RoutingAgent class and send Moderate Message. how to do is . thanks all.

use ILSpy tool see ModerateMessageByUserAction source code :

namespace Microsoft.Exchange.MessagingPolicies.Rules.Tasks
{
	[Serializable]
	public class ModerateMessageByUserAction : TransportRuleAction
	{
		private const string InternalActionName = "ModerateMessageByUser";
		private const string AddressDelimiter = ";";
		private SmtpAddress[] addresses;
		[LocDescription(Strings.IDs.ToAddressesDescription), LocDisplayName(Strings.IDs.ToAddressesDisplayName), ActionParameterName("ModerateMessageByUser")]
		public virtual SmtpAddress[] Addresses
		{
			get
			{
				return this.addresses;
			}
			set
			{
				this.addresses = value;
			}
		}
		internal override string Description
		{
			get
			{
				string text = RuleDescription.BuildDescriptionStringFromStringArray(Utils.BuildSmtpAddressStringList(this.Addresses), Strings.RuleDescriptionAndDelimiter);
				return Strings.RuleDescriptionModerateMessageByUser(text);
			}
		}
		protected override void ValidateRead(List<ValidationError> errors)
		{
			if (this.Addresses == null || this.Addresses.Length == 0)
			{
				errors.Add(new RulePhrase.RulePhraseValidationError(Strings.ArgumentNotSet, base.Name));
				return;
			}
			SmtpAddress[] array = this.Addresses;
			for (int i = 0; i < array.Length; i++)
			{
				SmtpAddress smtpAddress = array[i];
				if (!smtpAddress.IsValidAddress)
				{
					errors.Add(new RulePhrase.RulePhraseValidationError(Strings.InvalidRecipient, base.Name));
					return;
				}
			}
			base.ValidateRead(errors);
		}
		internal static TransportRuleAction CreateFromInternalAction(Action action)
		{
			if (action.get_Name() != "ModerateMessageByUser")
			{
				return null;
			}
			List<SmtpAddress> list = new List<SmtpAddress>();
			string stringValue = TransportRuleAction.GetStringValue(action.get_Arguments().get_Item(0));
			string[] array = stringValue.Split(new string[]
			{";"
			}, StringSplitOptions.RemoveEmptyEntries);
			string[] array2 = array;
			for (int i = 0; i < array2.Length; i++)
			{
				string text = array2[i];
				SmtpAddress item = new SmtpAddress(text.Trim());
				list.Add(item);
			}
			if (list.Count == 0)
			{
				return null;
			}
			return new ModerateMessageByUserAction
			{
				Addresses = list.ToArray()
			};
		}
		internal override Action ToInternalAction()
		{
			StringBuilder stringBuilder = new StringBuilder();
			SmtpAddress[] array = this.Addresses;
			for (int i = 0; i < array.Length; i++)
			{
				SmtpAddress smtpAddress = array[i];
				if (!smtpAddress.IsValidAddress)
				{
					throw new ArgumentException(Strings.InvalidRecipient, "Addresses");
				}
				string value = smtpAddress.ToString();
				if (string.IsNullOrEmpty(value))
				{
					throw new ArgumentException(Strings.InvalidRecipient, "Addresses");
				}
				if (stringBuilder.Length > 0)
				{
					stringBuilder.Append(";");
				}
				stringBuilder.Append(value);
			}
			ShortList<Argument> shortList = new ShortList<Argument>();
			shortList.Add(new Value(stringBuilder.ToString()));
			return TransportRuleParser.Instance.CreateAction("ModerateMessageByUser", shortList);
		}
	}
}

Anything is Possible！