My company sends out emails to our users through a 3rd party service (SendGrid) with a reply to address that comes to my Google Apps email account. The emails are sent out individually to each user after they perform a certain action. The emails all have the same subject and are sent from the same user (the user we asked our users to add to their address book when they signed up to try to avoid getting trapped in spam).
So the problem is that all the user replies to these emails end up in one thread, which is hard to manage (it's a bunch of individual conversations, not one large group conversation). Can anyone enlighten me about what I need to do to make these replies not group ? Is there an email header I can set when generating these emails on SendGrid to indicate a unique message thread or something? I'd really like to not have to try to create a unique subject for each user.
As a side note, also using SendGrid, I directly send myself certain emails with the same subject and from the same user, they show up in different threads. I'm not setting anything differently in the headers.