A bit of background:
Users in our company have multiple emails addresses... all in the form of UserID@domain.com... although there are mutliple different domains for each user, varying dependiong on departments, etc. Unfortunately there is no 'catch-all' domain, so from the userID alone it is not possible to send an email to that user, you need to either use the GAL (i.e. outlook) or know the exact department (and therefore the correct domain) to use.
I need a way to send emails to a user based on their logon details (i.e. from the 'windows authentication' information of an ASP.NET page or whatever), resolving automatically the correct domain of their primary SMTP email address.