ConversationIndex. The first 22 bytes will be the same for all messages in a
thread. Note that it won't work too well for the messages received from
outside of your Exchange server. Outlook ignores the "in-reply-to" headers.
From MSDN:
Tracking Conversations
Conversation tracking is collecting responses to a message. Clients should
set two properties that aid in tracking conversations:
PR_CONVERSATION_TOPIC
PR_CONVERSATION_INDEX
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 property.
PR_CONVERSATION_INDEX indicates the position of the message within a
particular conversation. It is a client's reponsibility 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:
a.. One reserved byte. Its value is 1.
b.. Five bytes for the current system time converted to the FILETIME
structure format.
c.. Sixteen bytes holding a GUID, or globally unique identifier.
d.. Each child block is composed of 5 bytes, divided as follows:
e.. 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.
f.. 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.
g.. Four bits containing a random number generated by calling the Win32
function GetTickCount.
h.. 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 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, the message
store provider can use the default value, or the value of the
PR_SENDER_ENTRYID property. Likewise, if you do not set
PR_ORIGINAL_AUTHOR_NAME or PR_ORIGINAL_SUBMIT_TIME, these properties can
default to the values of the PR_SENDER_NAME and PR_CLIENT_SUBMIT_TIME
properties, respectively.
Dmitry Streblechenko (MVP)
http://www.dimastr.com/
OutlookSpy - Outlook, CDO
and MAPI Developer Tool
