This is slightly off topic, but now I'd like to see Apple come out with a spam marker for the iPhone like in Apple Mail. I hate having to scroll through hundreds of email messages, 90% of which are spam that need to be deleted. It takes up sooooo much time!<
i agree. there are a couple of things you can try though,
IF you use imap, you could leave a mac either at home, or in the office, with apple mail, and possibly spamsieve? filtering your said account, and in theory, this would update your phone with less junk.......
secondly i have found the junk provision in google mail very good - something .mac mail needs to take a long hard look at IMHO. the "junk" it catches does not make it to your in box.
Thirdly if you use pop mail rather than imap, this may not work but what you COULD do, given the data bandwith issues of the iphone when on the road away from wifi, is set up a new account with google, for the iphone, have your GOOD mail forwaded or redirected from apple mail, and as it will have been "vetted" by google, apple mail and potentially spam sieve, it should cut the load considerably.
I agree it's extreme and will take some setting up, but needs must etc etc......
you can also get google to let you "send" mail as who you really are too - so if you have a domain name, register it and set as your default email account, and no-one will be any the wiser.......
hope that helps