I was able to set the MAPI conversationTopic and conversationIndex properties using the tips here and the code: '', _įor the ConversationIndex property, for example. This is not a complete answer, but it is too long for a comment. ORDOItem.ConversationTopic = incomingMail.Subjectĭebug.Print 'Trying to change conversation index.

Set oRDOItem = oRDOSess.GetMessageFromID(incomingMail.EntryID, )ĭebug.Print 'Trying to change conversation topic. Set oRDOSess = CreateObject('Redemption.RDOSession') Luckily, setting the Index to Null apparently makes Outlook pay attention only to the topic, so we don't need to re-calculate a new index.ĭebug.Print 'Creating Redemption Object. Otherwise they are still not grouped, even with same topic. While apparently ConversationTopic is used at first for grouping messages, also ConversationIndex plays a role in grouping: It does not only carry the sorting time stamp, but the first bytes are a conversation code that must match across all emails of a conversation. I was able to solve this myself by using Redemption to get write-access to the MAPI properties of ConversationTopic and ConversationIndex.

How to edit outlook identity