Go to Mailwasher>>Help>>Registration and remember the key that is displayed in the registration screen. Click the 'Renew Subscription' button and you will be taken to a web page where your license key is to be renewed. Check the key to be renewed and, if it is not displayed, click the 'Your Products' tab and it should be displayed. Now with the key to renew checked, click the 'Renew' button. You will be taken to the shopping cart. Scroll down and complete your payment details and submit.

Alternatively, you can login and enter your email address and password (if you don't know your password, request it via the option on the same page) and then proceed to the 'Your Products' tab.