Specific & Variable Redirects after Login

Hello,

Many apologies if this has been covered elsewhere, but I have searched through the forums and have not been able to find a previous entry that is similar to my situation.

My situation is pretty simple at first: I have User Role A that needs to go to Page A after login and User Role B that needs to go to Page B after login.

That part is simple and straightforward. I already have written code that can accomplish that, and there are any number of great plug-ins that do the same, too.

The core of my problem is that the client I have built a WordPress website for has started sending out emails to the user base which directs them to specific content or pages (i.e., an email with a link to an online newsletter or a special page).

So, my question:

How do I accommodate this variable redirect?

if User Group A => Page A, else
if User Group B => Page B, else
{link from email} => redirect to referring page

Is there any such plugin that can handle this, or does anyone know of a set line of code that would be usable?

Cheers, and many thanks in advance!