you know maizy they probably dont, can you imagine the man hours involved in just snooping through every persons email for no reason? they will do it if they are investigating a person for crimes, not just a sunday afternoon chuckiling at peoples email.
the government are quite welcome to go through my mail or look in my window, I have nothing to hide from them. please bear in mind that they cannot go through billions of emails, they would not be able to have time to work let alone enough staff to do there normal duties.
I would imagine they would access the email of the people they are tipped off about, like all those guys who had joined that paedophile group, they tracked them via their bank account details, would you prefer that they were not caught?
if you have nothing to worry about then I wouldnt worry, they are not interested in being nosey they are trying to cut serious crime