sendmail question

[Tim Wunder]

Having trouble finding the answer to this one, I know this has been 
discussed on the list before, but I haven't come up with the magic 
search string to find it...

How do I get sendmail to forward all outgoing mail thru my ISP's SMTP 
server? My IP address gets blocked by AOL and Comcast because it's 
dynamic, so sendmail can't send mail directly there. Since this is the 
automatic re-direction of e-mail sent to a domain name I'm hosting, 
manually choosing or configuring the SMTP server in the MUA is not an 
option (I already do that).

Thanks,
Tim