If you were a .Mac subscriber before the launch of MobileMe, you had a username@mac.com email address.  Now that we have converted to MobileMe, you have also been granted a username@me.com address.  These email addresses are aliases of one another, so they are one and the same and share the same inbox.  You can choose to use either email address to send and receive mail on your computer, iPhone, or iPod touch and set up your MobileMe Contact and Calendar syncing.

Continue reading here:
MobileMe: Using your mac.com and me.com email addresses

Similar Posts:

• MobileMe: Syncing calendar subscriptions and CalDAV calendars
• MobileMe: iPhone/iPod touch mail only updates when a new message is received or when checking mail manually, if Push is enabled
• Overview of syncing iPhone or iPod touch with your computer
• Sync Services: Advanced troubleshooting for contact and calendar syncing
• MobileMe: System Status says members may have trouble with automatic syncing, new mail notifications, and Find My iPhone