Reason why the person would use a web page instead of outlook to do it in the first place? Sounds funny to me! You will not get around the character limit with a GET. You might be able to find some activeX control that does this. I am not sure about that.
The reason a person needs to do this from a web page is that the list of users returned is one that will be determined through interaction with the web application. You will have no way of knowing who these people are until the web app returns you the list it compiles. Then, since you are already in the web application, being able to select just those users you want and just click a button that says send email or schedule meeting is a FAR more seemless experience for the user. It also makes for a much better and less error prone process than seeing all those names and then having to open Outlook and sit and enter them all into the To field, and then sit and enter text into the subject line (which we want to have some control over anyway), and then sit and enter information into the body that we could prepopulate, etc.
You will not get around the character limit with a GET.
If this is done on the client side, there is no issue with a GET because we aren't going to be using one to open the outlook window.
You should be able to do all of this on the server without involoving the user's version of outlook. There is ways to hook VB.NET/C# into Oulook to do all of this.
We need to allow the user to use outlook though in order to manually pick a time that is most convenient for them, etc. If we do outlook stuff on the server, won't the user be unable to see it? We need the user to be able to interact with outlook windows on their own machine (especially since they need support for adding additional people to the email that may be in their address book), and I would assume for all those reasons that they need to have their local copy of Outlook running with a window open on their own, local machine.
If anyone else has any ideas, it would be greatly appreciated!