Small addition to previous great answer. In case if anyone else will also need C# implementation of algorithm used to retrieve ConversationID from ConversationIndex/ConversationTopic:
private const int c_ulConvIndexIDOffset = 6;
private const int c_ulConvIndexIDLength = 16;
private string GetConversationId()
{
var convTracking = GetMapiPropertyBool(PR_CONVERSATION_INDEX_TRACKING);
var convIndex = GetMapiPropertyBytes(PR_CONVERSATION_INDEX);
byte[] idBytes;
if (convTracking
&& convIndex != null
&& convIndex.Length > 0)
{
// get Id from Conversation index
idBytes = new byte[c_ulConvIndexIDLength];
Array.Copy(convIndex, c_ulConvIndexIDOffset, idBytes, 0, c_ulConvIndexIDLength);
}
else
{
// get Id from Conversation topic
var topic = GetMapiPropertyString(PR_CONVERSATION_TOPIC);
if (string.IsNullOrEmpty(topic))
{
return string.Empty;
}
if (topic.Length >= 265)
{
topic = topic.Substring(0, 256);
}
topic = topic.ToUpper();
using (var md5 = new System.Security.Cryptography.MD5CryptoServiceProvider())
{
idBytes = md5.ComputeHash(Encoding.Unicode.GetBytes(topic));
}
}
return BitConverter.ToString(idBytes).Replace("-", string.Empty);
}
GetMapiProperty...() is a helper functions which just retrieve required MAPI property and cast result to appropriate managed type