I found some problems with the software that I used for mail forwarding.
GetMail is not forwarding any attachment in the mail. I am now using ERC (Email Redirecting Client) instead. It works perfectly for me.
Free SMTP Server only send 10 emails per day after some period of used. I finally figured out how to enable email relaying on my Sun machine by specifying my PC's IP address in /etc/mail/relay-domains .