read property inside message

[Lattis]

I am trying to achieve the following:

I have a .net application which stores emails in a sql database. These
messages are given a unique number which is used to store a number of
metadata in sql tables. I would like a way to SMTP a message stored in my
database to an exchange 2007 account which will be accessed by an outlook
2007 client. The email message should have the unique key stored inside it in
such a way so that the outlook client will read and display it as a column in
the main view.

My idea was to add something like <x-MailKey=333333> which I would then read
somehow from outlook so that I can display it as a column

Any ideas??

Thanks

Lucas