Here are a few things to look at:
- Ensure that your ISP permits mail server relay - i.e. using a non-ISP SMTP server.
- Ensure that your router isn't blocking outbound mail TCP/IP Port 25; doubt this will be your issue
- Try setting the smtp mail server port for gmail to: smtp.gmail.com:587
- Try account mode with the account name set to: recent:<yourusername>@gmail.com
Many server now require SSL for Incoming E-mail as well as for Outgoing e-mail. If all else fails, set the SMTP server to the ISP SMTP server, change to Anonymous, and set the Sender Email to the one provided by your ISP.
HTH,