Tracking Conversations

Applies to: Outlook 2013 | Outlook 2016

Conversation tracking is collecting responses to a message. Clients should set two properties that aid in tracking conversations:

  • PR_CONVERSATION_TOPIC (PidTagConversationTopic)

    PR_CONVERSATION_TOPIC is the normalized subject of the message, the subject without the prefix strings. Set this property to the value of the message's PR_NORMALIZED_SUBJECT (PidTagNormalizedSubject) property.

  • PR_CONVERSATION_INDEX (PidTagConversationIndex)

    PR_CONVERSATION_INDEX indicates the position of the message within a particular conversation. It is a client's responsibility to set PR_CONVERSATION_INDEX for each outgoing message, whether it is a new message, a forwarded message, or a reply. Clients can set this property manually or call ScCreateConversationIndex, a utility function provided by MAPI.

ScCreateConversationIndex generates the value of a conversation index for any outgoing message. ScCreateConversationIndex implements the index as a header block that is 22 bytes in length, followed by zero or more child blocks each 5 bytes in length.

The header block is composed of 22 bytes, divided into three parts:

  • One reserved byte. Its value is 1.
  • Five bytes for the current system time converted to the FILETIME structure format.
  • Sixteen bytes holding a GUID, or globally unique identifier.

Each child block is composed of 5 bytes, divided as follows:

  • One bit containing a code representing the difference between the current time and the time stored in the header block. This bit will be 0 if the difference is less than .02 second and greater than two years and 1 if the difference is less than one second and greater than 56 years.

  • Thirty one bits containing the difference between the current time and the time in the header block expressed in FILETIME units.This part of the child block is produced using one of two strategies, depending on the value of the first bit. If this bit is zero, ScCreateConversationIndex discards the high 15 bits and the low 18 bits. If this bit is one, the function discards the high 10 bits and the low 23 bits.

  • Four bits containing a random number generated by calling the Win32 function GetTickCount.

  • Four bits containing a sequence count that is taken from part of the random number.

If you choose to set the conversation indexes of messages manually, consider the following suggestions:

  1. Keep differences in the respondents' time zones transparent; use UTC times rather than local time.

  2. Indent each conversation group by the same amount.

  3. Sort responses to the same message date.

  4. Separate threads started at different times that happen to share the same topic.

  5. To implement a categorized sort so that messages are grouped by topic, sort by PR_CONVERSATION_TOPIC first and then by PR_CONVERSATION_INDEX. To present the results of the sort, set the PR_DEPTH (PidTagDepth) property to 0 for messages with a conversation index that is 22 bytes in length. Then, for every 5-byte increment in the length, increment the value of the PR_DEPTH property by one.

The PR_ORIGINAL group of properties can also be used for conversation tracking. Set these properties to link reply or forwarded messages to the original message. All of the PR_ORIGINAL properties are optional. If you do not explicitly set, for example, PR_ORIGINAL_AUTHOR_ENTRYID (PidTagOriginalAuthorEntryId), the message store provider can use the default value, or the value of the PR_SENDER_ENTRYID (PidTagSenderEntryId) property. Likewise, if you do not set PR_ORIGINAL_AUTHOR_NAME or PR_ORIGINAL_SUBMIT_TIME (PidTagOriginalSubmitTime), these properties can default to the values of the PR_SENDER_NAME (PidTagSenderName) and PR_CLIENT_SUBMIT_TIME (PidTagClientSubmitTime) properties, respectively.