"Seriously, anyone who sends email and expects nobody else to read it, and their privacy rights to be protected is a bit of an idiot"
I completely agree. It is likely that your email will have passed, plain text, through multiple SMPT servers before reaching you. Anyone on one of those servers, or sat in between with a packet sniffer, could have read them.
Email is not secure. Realy, the only thing which can make it so is encryption. And, as mentioned above, most people cant be bothered.
Things get even worse when you start looking at VoIP. Unencypted audio packets, floating accross the net. I wouldnt be surprised if cops were allowed to capture these without a warrant, as they are floating around where anyone can see them.
It is up to YOU to ensure you have a secure communication channel. If you haven't, don't say anything which might incriminate you.