As i said before:
Go to the WEBSITEFORGE.COM site, login with your account and change the MX record in DNS configuration.
This is the fastest and rsecure way.
If you can't do it you can ask websiteforge's support to do it for you.
If it can't be done, i don't know the policy of websiteforge for domain dns management, than you have to retransfer DNS management to REGISTER.COM and recreate all dns entries there. This is done on the register.com site in DNS control panel when you login with the user you made to register the domain name.