Causes HTML emails to be sent as plain text

OK, so this one is odd…

Multiple plugins may send HTML email notifications but I experienced this issue consistently with HTML emails sent from Gravity Forms and from WPMU DEV Defender Pro weekly notification emails.

When this plugin is active, the emails come through looking like HTML converted to plain text, but I think they’re technically still text/html content type. When I view these emails in your plugin’s logged emails viewer, they render properly, but the emails actually sent by the website are not rendered properly.

I experienced this issue on multiple websites at different web hosts that use different email sending services.

When this plugin is deactivated, the issue is no more.

Please investigate.