Sjazbec, I have to disagree based on experience. Since activatingiCloud on my iPhone 4 (updated to IOS 5) and the mail app on my newiMac (running LION) last Tuesday, NONE of my email shows up in theyahoo inbox via the mail app on my iphone. ALL of my email is visiblefrom the yahoo website page through Safari. NONE of the mail sent frommy iPhone appears in the Sent folder on Yahoo.
Until last Tuesday, none of this happened with my iPhone 4.
Onmy iPhone, I went to Settings->iCloud and deleted my iCloud account(option available if you scroll all the way down) completely, andvoila, lo and behold, instantly, all my email since Tuesday magicallyappears in my inbox.
I admit it's likely I have noconcept as to how iCloud is supposed to work. Of course, I bought bothLion and IOS5 and neither came with any explanation.