"Immediately copy messages" option cannot be checked in IE7

> Using Internet Explorer 7, in a user's 'Routing' options, I am unable to check the "Immediately copy messages already in this user's Inbox to assistant(s)" box.

Have you tried with a different web browser?

The web page should pop up a confirmation window when you check that box. It may be that some web browser setting is preventing it from displaying that window.

In other versions of Internet Explorer, there's an option "Allow websites to prompt for information using scripted windows" under Internet Options -> Security Tab -> Custom Level. That must be enabled. There may be a similar option in IE7 (however, note that IE7 is not a supported web browser for use with VPOP3).