Get a Mandrill account and do your SPF and DKIM – it has a great interface to check them for when they’re ready to use.
1. Look for wpMandrill plugin for your WP emails
2. Configure the Wysija SMTP config in much the same way as EE
then you’re set to go.
You’ll probably eventually want to style your plain-jane WP emails to use HTML and then insert useful links in those email. Obviously you might not either but I did as it’s another way to advertise affiliate links, my shop etc. The Templating took me a little while to suss out but with the help of their support, I just created a HTML template and inserted some ‘content’ tag and I was all set – freaking beautiful and 12000 per month free emails.
Recommended definitely and works great with Wysija too