Unable to view the buttons on iphone ios 5

Hi,

I m unable to view the some buttons on Iphone with IOS 5. There is a image in the email when u click on the image it will show the "open" link button. this button i am unable view in Iphone with IOS 5. 

 Same thing i am able to view in IPhone with out IOS 5.

 Please help me.

If there is any settings for Iphone with IOS 5 to enable the buttons on emails.