You need to enable or disable authentication of emails as the case might be. Settings in Outlook Express/Windows Mail are express you don't need to do anything.
Peter
root@jaribu:/usr/local/squid/logs # host -tmx jambo.co.ke
jambo.co.ke mail is handled by 20 mail.jamboworld.com.
jambo.co.ke mail is handled by 10 mail.jambo.co.ke.