LinkedIn Intro introduced in October last year, injecting HTML code into the top of the emails you receive on your iPhone so you could view someones LinkedIn profile alongside the message they have sent you. This feature came at a huge cost for privacy. To get it to work, LinkedIn required you to change the settings of your iPhone to connect via LinkedIn’s proxy server. This meant that LinkedIn would be acting as a man-in-the-middle for all your email conversations.”]
Source: https://grahamcluley.com/linkedin-shutting-controversial-intro-service-good-news-care-privacy/