Software Deployment

I'm not sure I totally know what you want to do, but you could hijack the outlook shortcut to run a script that looks for what you require to use the new profile. Maybe something like a PST not existing in the logged in user's profile. Once you've done what you need to do in your script, then set the outlook shortcut to default.

how are you deploying the profiles?
AFAIK there are 3 methods: PRF files, REG keys, autodiscovery

maybe we can help you if you give us some more details

Is the new server running Exchange 2007 or higher (hard to see why a new server wouldn't be...)? If that's the case, wouldn't Outlook 2007 use Auto Discovery?

I'm using PRF file with the help of Office Customizatoin tool. We have Exchange 2007 in the environment.

Finally I removed the old profile(by deleting the registry key) and created new one with required changes. It worked fine for workstation which are newly reimaged.

But challenge is still there with existing machines, where multiple users are created with outlook profile(old setting/not migrated to new exchange server).

i didnt use PRF files much and don't know all the pitfalls and details coming it.
but there are 2 extensive msdn articles about that topic. did you already read them?
http://technet.microsoft.com/en-us/library/cc179062.aspx
http://technet.microsoft.com/en-us/library/cc178945%28office.12%29.aspx

they describe a difference between just applying initial profiles or modify existing ones. maybe you need a seperate "modify PRF" file for your task