application choice for outbind

In a message from a listserv, all the messages appear as "OUTBIND://******"
... and when I clicked on them, a dialog appears asking me to choose an EXE
file..

So I did. I chose Outlook. Seemed like the thing to do, to have Outlook
open those links.

Now when I click on any OUTBIND links, Outlook opens another instance.
HOW can I change this, and WHAT should I change it to (maybe a browser?)

THANK YOU!!