A simple plugin that allows you to identify which pages should have HTTPS enforced. All other pages will have HTTP enforced.
Plugin Tag: https
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SSL Atlas – Free SSL Certificate & HTTPS Redirect for WordPress
Helps install a free SSL certificate, fixes mixed content, insecure content by redirecting to https, and forces SSL on all pages.
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Double Slash Domains
This plugin removes the http/https schema from urls inside the blog source code and replace them with double slash.
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ElasticEmail Plugin
Reconfigures the wp_mail() function to send email using HTTPS (via Elasticemail) instead of SMTP and creates an options page to manage the settings.
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Flex SSL
Enables SSL & forces HTTPS on WordPress, updating URLs & adding security headers. Supports reverse proxies & soon integrates Let's Encrypt.