I have seen a number of articles on the web that highlight the fact that iPhone has not built in junk mail filter. This would be a relatively simple thing to implement - so why has Apple not done it? Well I think the answer is simple. Because iPhone supports IMAP mail accounts, and many IMAP servers including Apple's .Mac has built in, online junk mail filtering, it makes little sense to have it crammed into the iPhone. If you are a .Mac subscriber, and have enabled junk mail filtering on the .Mac web mail interface, this will be reflected in your iPhone as well. All your junk mail goes to the 'Junk' folder on the iPhone, exactly mirroring the web mail interface - see the images below. By the way, the originators of the junk mail on these images better pack up their act :-)