The showforwards command takes the machines listed in an accounts -m and retrieves your .forward files from those machines that can receive mail for you. It lets you see at glance where all your mail is going. Use this command whenever you have new accounts installed or whenever you suspect your mail isn't being delivered properly to verify that your .forward files are correct.
See the man pages for showforwards and forward for more details, including proper syntax for your .forward files.