Spam or junk email is a common threat to most of us in the wired world. Though they are easy to block from both your desktop computer or webmail, the difficulty here is synchronizing which messages to block, especially if you access your email from more than one client, such as Mail.app, your iPhone or the Web. Spam emails also count against your server's storage space, and you could run out of storage if your inbox is filled with unwanted and unsolicited messages.
Assuming you've enabled spam filtering in MobileMe email, and you use the Mail.app application on OS X, the emails in the junk folder may not necessarily be synced, and you might find that your MobileMe mail inbox is filled with mail that Mail.app has classified as junk. You would need to set your Mail.app settings accordingly, so that the application sends the correct emails to the spam folder, and that this is in sync with the server's contents.
- Open Mail.app on your Mac.
- Click "Preferences." from the Mail menu on the menu bar.
- Click "Junk Mail." Make sure the check-box for "Enable junk mail filtering" is checked.
- Select "Accounts."
- Select the account that corresponds to your MobileMe email account.
- Select the "Mailbox Behaviors" tab. Under this tab, you can find the "Junk" setting beside the trash bin icon. Check the box that corresponds to "Store junk messages on the server."
Also, if you have ticked the check-box for "Automatically move messages marked as junk to the Junk folder" in MobileMe email settings, you should do the same in Mail.app. Under the "Junk Mail" tab in Mail.app preferences, tick the radio button for "Move it to the Junk mailbox" under the "When junk mail arrives" setting.
When these settings are in place, all messages that are marked as junk by Mail.app will be placed in the same Junk folder on the MobileMe server. This means that when you trash messages from the junk mail folder, these will also be removed permanently from the server, and consequently, from all other devices or Mail.app profiles you access your email from.
You need to replicate these settings with other Mail.app profiles where you access your MobileMe email from, to be sure that every time you connect to MobileMe, the messages that are classified as junk by Mail.app would also be moved to the Junk Mail folder on the MobileMe server. This should also apply if you use Mail on your iPhone.
Remember that messages in your junk mail folder still count against your total email storage space. So be advised that you should review your junk folder regularly for false positives (for valid emails that have been classified as spam). And remember to clear your junk folder regularly, so that these don't accumulate and eat up your storage.
Another good tip would be to avoid giving out your MobileMe email indiscriminately. It might be a good idea to keep a separate, free, email address for subscribing to e-groups, and for signing up for online services. And don't publish your email on your blog or other websites where spam-bots can easily harvest them. This way, if ever you get spam emails, it won't be sent to your precious MobileMe account.