Question over Edge?? plz help

Hi,,
I am in india... have unocked iphone.. working really well..
One question. I want to subscribe for edge so i can see my mails all the time.. just want it for mails..

The question is , here we are charged per KB downloads...If i tune in my gmail... and i get a mail which is 4 mb or something.. will i straight away be charged for 4MB or will be charged only if i view the mail... like if i delete it before opeiing the mail will i be charged...