Hello,
It is far easier to help you troubleshoot the problem if you provide the real complete IP addresses.
Also, which mail server software (MTA) are you running?
Without being able to check it myself my first guess is that the port is not open.
Try doing a telnet to 80.x.x.x 25 . Do you get a response?
If not, does your ISP block incoming connections on port 25?
Double check that your network NAT's and firewalls are configured correctly.
Do you get any error messages?
Is that IP address that you are sending from allowed to relay though 80.x.x.x ? You will either need to configure it to allow relaying based on IP address, or configuring some form of smtp authentication so that you can use a username and password to let it know that you are allowed to relay mail through your mail server from the remote hosts.
-Raymond