You can’t tell Siri to read your emails and web pages, but you can use Apple’s iOS voiceover feature to read your emails and web pages out loud 
More info here:
Tip: How to Make Siri’s Twin, VoiceOver, Read Your Email on iPhone | iSourcehttp://isource.com/2011/11/12/tip-how-to-make-siris-twin-voiceover-read-your-email-on-iphone/That’s odd, I thought, I know I could get my 3GS to read my emails to me! You may be curious how. It’s an Accessibility setting called VoiceOver. So what I tried…
Will Siri ever read emails and other selected texts from web pages to you? – Quorahttp://www.quora.com/Will-Siri-ever-read-emails-and-other-selected-texts-from-web-pages-to-youSiri itself won’t do this, at least not right now, however iOS has already supported VoiceOver for some time, which you can configure under the Accessibility settings…
Apple – iOS – Siri Frequently Asked Questionshttp://www.apple.com/ios/siri/siri-faq/Siri is the intelligent personal assistant that helps you get things done just by asking. It allows you to use your voice to send messages, schedule meetings, place phone calls,…
Siri can’t read emails!? Only text messages? – MacRumors Forumshttp://forums.macrumors.com/showthread.php?t=1246704I just watched a Macworld review video where they say that Siri cannot read emails, it can just tell you how many unread emails you have, but it can read you txt messages and…
