Please find my first web service client that i tried couple of months earlier that creates an e-mail item in the Sent Items folder. You can use Microsoft Visual Studio 2005 to create a simple Exchange Web Services client application like this.

   1:  using System;
   2:  using System.Net;
   3:  using System.Security.Cryptography.X509Certificates;
   4:  using System.Net.Security;
   5:   
   6:  // The ExchangeWebServices namespace was created by using Visual Studio // 2005 and the Add Web Reference wizard.
   7:  using ExchangeWebServices;
   8:   
   9:  namespace Devas_First_WebService
  10:  {
  11:      partial class Program
  12:      {
  13:          static void Main(string[] args)
  14:          {
  15:              ServicePointManager.ServerCertificateValidationCallback =
  16:              delegate(Object obj, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
  17:              {
  18:                  // Replace this line with code to validate server 
  19:  // certificate.
  20:                  return true;
  21:              };
  22:   
  23:              // Identify the service binding and the user.
  24:              ExchangeServiceBinding esb = new ExchangeServiceBinding();
  25:          // Provide the Network credentials - username, password, domain
  26:              esb.Credentials = new NetworkCredential("<username>", "<password>", "<domain>");
  27:          // Provide the Exchange Web Service (URL)
  28:              esb.Url = @"https://<FQDN>/EWS/Exchange.asmx";
  29:   
  30:              // Create the CreateItem request.
  31:              CreateItemType createEmailRequest = new CreateItemType();
  32:   
  33:              // Specifiy how the e-mail will be handled.
  34:              createEmailRequest.MessageDisposition = MessageDispositionType.SaveOnly;
  35:              createEmailRequest.MessageDispositionSpecified = true;
  36:   
  37:              // Specify the location of sent items. 
  38:              createEmailRequest.SavedItemFolderId = new TargetFolderIdType();
  39:              DistinguishedFolderIdType sentitems = new DistinguishedFolderIdType();
  40:              sentitems.Id = DistinguishedFolderIdNameType.sentitems;
  41:              createEmailRequest.SavedItemFolderId.Item = sentitems;
  42:   
  43:              // Create the array of items.
  44:              createEmailRequest.Items = new NonEmptyArrayOfAllItemsType();
  45:   
  46:              // Create a single e-mail message.
  47:              MessageType message = new MessageType();
  48:              message.Subject = "Daily Report";
  49:              message.Body = new BodyType();
  50:              message.Body.BodyType1 = BodyTypeType.Text;
  51:              message.Body.Value = "(1) Handled customer issues, (2) Saved the world.";
  52:              message.Sender = new SingleRecipientType();
  53:              message.Sender.Item = new EmailAddressType();
  54:              message.Sender.Item.EmailAddress = "user1@example.com";
  55:              message.ToRecipients = new EmailAddressType[1];
  56:              message.ToRecipients[0] = new EmailAddressType();
  57:              message.ToRecipients[0].EmailAddress = "user2@example.com";
  58:              message.Sensitivity = SensitivityChoicesType.Normal;
  59:   
  60:              // Add the message to the array of items to be created.
  61:              createEmailRequest.Items.Items = new ItemType[1];
  62:              createEmailRequest.Items.Items[0] = message;
  63:   
  64:              try
  65:              {
  66:                  // Send a CreateItem request and get the CreateItem 
  67:  // response.
  68:                  CreateItemResponseType createItemResponse = esb.CreateItem(createEmailRequest);
  69:                  ArrayOfResponseMessagesType responses = createItemResponse.ResponseMessages;
  70:                  ResponseMessageType[] responseMessages = responses.Items;
  71:   
  72:                  // Access the response messages.
  73:                  foreach (ResponseMessageType respMsg in responseMessages)
  74:                  {
  75:                      if (respMsg.ResponseClass == ResponseClassType.Error)
  76:                      {
  77:                          throw new Exception("Error: " + respMsg.MessageText);
  78:                      }
  79:                      else if (respMsg.ResponseClass == ResponseClassType.Warning)
  80:                      {
  81:                          throw new Exception("Warning: " + respMsg.MessageText);
  82:                      }
  83:   
  84:                      // Check to determine whether the response message is the correct type.
  85:                      if (respMsg is ItemInfoResponseMessageType)
  86:                      {
  87:                          ItemInfoResponseMessageType createItemResp = (respMsg as ItemInfoResponseMessageType);
  88:                          ArrayOfRealItemsType aorit = createItemResp.Items;
  89:   
  90:                          foreach (ItemType item in aorit.Items)
  91:                          {
  92:                              if (item is MessageType)
  93:                              {
  94:                                  MessageType myMessage = (item as MessageType);
  95:                                  Console.WriteLine("Created item: " + myMessage.ItemId.Id);
  96:                                  Console.ReadLine();
  97:                              }
  98:                              // If needed add the logic to check and cast for all other types.
  99:                          }
 100:                      }
 101:                  }
 102:              }
 103:              catch (Exception ex)
 104:              {
 105:                  Console.WriteLine(ex.Message);
 106:                  Console.ReadLine();
 107:              }
 108:          }
 109:      }
 110:  }
 
Reference: Creating an Exchange Web Services Client Application