1) You have to opt-in and install Intro before you see LinkedIn profiles in any email.

2) Usernames, passwords, OAuth tokens, and email contents are not permanently stored anywhere inside LinkedIn data centers. Instead, these are stored on your iPhone.

3) Once you install Intro, a new Mail account is created on your iPhone. Only the email in this new Intro Mail account goes via LinkedIn; other Mail accounts are not affected in any way.

4) All communication from the Mail app to the LinkedIn Intro servers is fully encrypted. Likewise, all communication from the LinkedIn Intro servers to your email provider (e.g. Gmail or Yahoo! Mail) is fully encrypted.

5) Your emails are only accessed when the Mail app is retrieving emails from your email provider. LinkedIn servers automatically look up the "From" email address, so that Intro can then be inserted into the email.

For the entire post: http://engineering.linkedin.com/mobile/linkedin-intro-doing-impossible-ios#!