DKIM Installer
DKIM Installer is a Prestashop plugin that allows you to add DKIM signatures to your outgoing emails, helping you improve email deliverability and protect against spam.
addons.prestashop.com
I think is a must have for PS 1.7, this module helps to get your DKIM keys from cpnel and use them at signatures to your outgoing emails. For PS 8 it comes integrated, and the problem from 1.7 with emails that are sent to spam was solved.