The email address can't be edited.
If the user's email address is incorrect, you'll have to remove the user and then create them again. Edit the user's name (for example, add "OLD" to the name), and then create the new user with the correct email address. You can then remove the old user from the Client Portal if required.
The user may only be removed if there are no outstanding Tasks linked to the client. If the email address had been initially entered incorrectly, prior to deleting the email address, delete any documents that are currently awaiting approval. If your client has changed their email address, do not delete documents that are published or signed.