If you want your client to open an email delivery notification and directly go to the lead they received in their Client Portal, you can do so by following the steps below:
The first thing you will need to do is set up your client portal. To assist you with that, you can review How To Configure Client Web Portal and How to Create Client Credentials for Web Portal.
Now that you have configured your portal and your client has access to the portal, you can put the URL into the email template that delivers to your client. You can edit this in the Template tab of your Delivery Method Details screen.
In the Template tab in your Delivery Method Detail screen, go to the Insert Hyperlink button.
Next, enter the text you wish to display for the link. For our example, we will use "New Lead". Then, in the address bar, you will add the field mapping
Once you have added the hyper link test, you can edit your template language for your customers.
Now you have a link that will open the lead in the client portal!