Here are a few troubleshooting tips:

Can you establish a simple telnet session to the DNS2Go mail server on port 25? From the DOS prompt type:

telnet mail.dns2go.com 25

If you are unable to connect through a telnet session, verify that you have port 25 open on any local routers or firewalls. If you do or are not running either of these, possibly your local ISP has begun blocking outbound port 25 connections. Typically when they do this, they only allow outbound port 25 connections to their email server.

You can attempt to telnet to mail.dns2go.com on port 110 and port 366. If you are able to connect to mail.dns2go.com on port 366, you can use ATRN instead of ETRN. This uses an authenticated session and transfers the email via SMTP on the same connection through port 366.

Either your local mail server would have to support issueing the ATRN protocol of your could use the XATRN client from the following URL: http://xatrn.panozzo.it/