.net - IIS Redirect From Specific Outdated URL?

One of my clients refers people to a certain URL. She prints the URL on physical letters, and the recipients have a few weeks to visit the URL and complete the task. Let's say that the URL she gives is:

[URL]

The problem is that I am switching Content Management Systems so the page she links people to will sit at a different URL. But since she physically prints the URL on letters there needs to be some overlap so people can visit the old URL and be redirected.

Here's where it gets tricky. In the new system the subdomain of www.department-a.domain.com actually forwards to www.domain.com/index/department-a.aspx

Which isn't a folder but an actual page- which makes redirecting tricky. It also means I can't simply recreate the folder structure and use a simple HTML Meta refresh/redirect. Essentially my question is:

Is there anyway in IIS to tell the server that when someone attempts to view the specific and no longer existent URL of "www.department-a.domain.com/folder/important-page.html" to redirect them to another location?