Sendmail client configuration to connect to ISP's SMTP server

[Aflatoon Aflatooni]

What configuration do I need to set in my freebsd.submit.mc in order to connect to the ISP's SMTP server?
The ISP is blocking all the emails unless it goes through their mail server, so I need my FreeBSD box to connect to the ISP's SMTP server for outbound emails.

The client also needs to be authenticated as well.

Please help

Thanks
Afi