Linking Web to Case and Contacts

Linking Web to Case and Contacts

For some reason, when I submit a case from the Web to Case form that is provided, it doesn't link the case to an existing account in CRM. Is this by design or am I doing something wrong? I would assume the case would be linked up via the email address.
Anyone see the same problem?
Thanks!
Stephen Crescenti
Email Cleaners, Inc.
stephen@emailcleaners.com