colinneagle (2544914) writes "LinkedIn's new feature, called Intro, basically uses Rapportive's technology to insert a banner into emails that show LinkedIn information about the person who sent them. So, users who get an email from a stranger can see the information that person has listed on LinkedIn without navigating away from the email. How this was accomplished seems pretty interesting, though. Rapportive's technology was once a Gmail plugin, but was banned from Gmail after a Google redesign. Making things even more difficult is that Apple's Mail app for iOS does not support plugins or extensions at all.
So LinkedIn built an API that "extends" the iOS mail app. Using a proxy server that speaks the IMAP protocol that most email providers employ, Intro tacks the banner featuring the sender's LinkedIn information onto the top of the message while the message is being forwarded from the device to the email provider. In this process, it also recognizes the specific device used to open it, and adapts its banner to meet its requirements. Then, using a CSS code response that is native on the mobile version of Safari, LinkedIn was able to make the Intro bar interactive, meaning users can click on it to find out more information about the sender."
Link to Original Source