Thanks Mary! I would also add that there are some stock email templates that include a link to the portal for the customer to use to sign in. An example is the CRM_CaseUpdateForCustomer template.
If you are creating or editing an email template you can add the link by using a merged field. The text you should include in the email template is http://urlforportal. This text will create a unique URL for each customer to use to login to their account. There are a few actions that you must use on the screen to get a merged field functioning properly. The best way to learn how these actions work is to copy, edit, and reverse engineer a screen such as the CRM_EditCase screen which has the appropriate email actions set up. Make sure to test out your email templates before you send them to your customers by sending yourself a test email to ensure that the merged fields all work properly.
Click here to learn more about merged fields and portal links in our Help Center.
- Jason