When you get a comment email from Crucible, the To: field in the header reads as

From: "Rosen, Dustin" <sourcecode@mydomain.com>
To: david.hergert@mydomain.com

If you want to contact the user using the email, if you click Reply, the resulting email comes up with the To: as 'Dustin Rosen'. You'd think it was emailing Dustin's email address, but its really emailing sourcecode@mydomain.com. (see From: field above). But I understand why the name in the From field is the person's name, because it looks nice in your inbox that this comment (in email form) came from that person.

So, I would recommend either either changing the From to actually be Dustin's email address, so if someone replies to an email, it actually goes to Dustin. This would make sense since Crucible currently doesn't appear to accept replies through email and add them as a reply-comment (would be a neat feature though). Or the other option would be to add a Reply-To header to the original email, and set it to 'sourcecode@mydomain.com' so that if someone clicks Reply, you will see in the To: field that its not going to the author of the comment, but rather back to the Crucible server (and so you should change it t go to the person you want, presumably the author of the original comment).