The email client is needed to ensure the Windows PC gets all the right certificates etc installed in the right places.
If you take a look at the PAC Display users guide (doc 1702. From within PAC Display, click Help->Manual), page 277 onwards deals with emails.
Step 7 on page 279 shows how to set up PAC Display to send the email in the background, with no user intervention, or to allow the user to edit the email before its sent.
In other words, depending on your email client, it will either just work, or you will need to tweak the email client settings to automatically send the email.