Outlook 2010 has a conversation grouping feature that can be pretty handy when you have a lot of different conversations headed to your inbox. However sometimes it gets confused.
Unfortunately it’s pretty poor at handling a few situations: when several different threads have the same subject and when the subject line is changed. In theory, there should be a way for Outlook to work around those limitations using standard emails headers, but it doesn’t. Maybe in 2012…
Recently I had several different email threads going at once with tens of emails a day for the same project. Unfortunately one of the participants had a spam filter that would append [!!SPAM] to nearly every subject line. If I didn’t correct the subject, we’d eventually get a subject like RE: [!!SPAM] Re: [!!SPAM] RE: You get the idea.
While you can change the subject of an email in your inbox, it’s still grouped into a separate conversation.
So I went looking and eventually found a tool called MFCMAPI that will let you poke into all kinds of hidden fields in Outlook. Make sure you get the 64bit version if you’re using the 64bit Outlook.
After starting a session and connecting, it gave me a list of mailboxes:

Double clicking my mailbox brought up this:

And double clicking on my inbox brought up a list of emails. If I double clicked on an email, it would open up in Outlook. However, just selecting the email would show a list of properties below:

I ended up editing PR_CONVERSATION_TOPIC and PR_SUBJECT:

The PR_CONVERSATION_TOPIC field is used by Outlook to group emails into the same conversation. As far as I can tell it can be nearly any unique string. I just changed it to remove the [!!SPAM] and the RE: since that’s what other messages already in the conversation used.
This has helped me quite a bit to get organized when I was being overwhelmed with emails. It’s probably not foolproof, so be careful what you change. I only changed the two fields and I’m not even sure what half the other ones are.
Now that I know which fields to change I was hoping to find or make a plugin that would do this from within Outlook automatically.



