I defined some custom fields for the Outlook mail message and it works OK.
User can enter the value into the field during the editing of a new message (using my addin).
I added the fields to the folders as well, so user can see the value of the field he entered later, inside his 'Sent Items' folder.
Now, when user A sends the message to user B, user B can see the value that user A entered - and I want to avoid this.
One way to do this is probably to subscribe to the NewMail event at recipient's side and clear the value.
But I'd like more if I could mark the field in such a way that the data in it isn't sent to the external recipient.
Is it possible?