from django.conf.urls import patterns, url
from yourapp.views import legacy_mandrill_click_tracking_redirect

urlpatterns = patterns('',
    # ...
    url(r'^track/click/(?P<mandrill_account>(\d+))/(?P<target_host>([a-z0-9.-]+))/?$',
        legacy_mandrill_click_tracking_redirect),
    # ...
)