I have a requirement like, User can view the section like a form on a click in email template.
One solution could be Configuring the DWA Direct web access. so it will open the form or on going assignment.
Other solution can be directly opening the pega portal using this trick :
https:///prweb/PRAuth/pega?UserIdentifier=<User_name>&Password=
Try using this URL it will open the appropriate portal the user has access.
Password should be Base64 encoded. you can also customize the authentication service as per your need and give the appropriate link in the email.