Really Simple SSL Pro - Optimizes your site for SSL

This requires the FREE version to be installed first.

Really Simple SSL pro contains an extensive scan for mixed content issues, access to premium support, HTTP Strict Transport Security and more!

Extensive scan which enables you to detect the source of mixed content that couldn’t be fixed automatically, with fix button
Premium email support (details)
HttpOnly and secure flags to make the cookies more secure
Improve security by enabling HTTP Strict Transport Security for your site
Submit your site to the HSTS preload list
Warning by email and in your SSL dashboard when your certificate is about to expire
Mixed content fixer for the back-end
Easy implementable security headers: X-Content-Type-Options, X-XSS-Protection, X-Frame-Options, Expect-CT, Certificate Transparency, No Referrer When Downgrade header, Content Security Policy. Read the security headers article for more info.