I'm having a problem where when I use a mail client to try to send mail through my ISPs mail server, the authentication fails. It is a pop3 account.

I have two routers. I have a d-link that has the default config, with passwords changed and etc. That doesn't have a firewall on it. I can send/recieve mail just fine with that.

However, I have a Cisco 806 broadband router that I have been using and like better.
This is the router I have problems trying to get the smtp to authenticate to send mail. I can receive just fine.

I called my ISP and they advised me to change my MTU. They recommend 1492, which is what it was. They said that some people have better luck with 1500. I have tried that too... and it still won't work.

I will post my config. If anyone notices a config error, please let me know.
I'm thinking there might be a problem with the firewall rules? Though... I don't know why. I allow ALL out, block ALL in. I have personal firewalls on each client to block individual apps on each client. So, I didn't put it on the router.

Its driving me nuts...

EDIT: In the config, you'll notice that on interface Dialer1, there is no mtu specified. I have corrected this. It won't however take the value 1500 as recommended by my ISP.