What happens if you connect in exactly the same way you used to connect, before you installed the ADSL Router? If all is well, it is certainly your Router that is causing the problem.
You could try setting the server addresses to your Router in Outlook Express (if you haven't already done so).
Open Outlook Express and select; Tools; Accounts; highlight one of your e-mail accounts and select Properties. Under the Servers Tab, enter your Router address in both the POP3 and SMTP server boxes. Many Routers use the default address;
but you will need to look at the Router information page, to find out the correct address for yours. Click apply; OK; and see if you can now access your e-mail.