Qmail outbound auth with smtproutes

[David McMahon <djm@xxxxxxxxxxxx>]

Sorry if this question has been answered, but I could not find it
in the list archive.

I run qmail(Linux) for a few domains on a comcast line. 
I had been smtproutes'ing everything through smtp.comcast.net
for a long time, but recently moved to a new comcast location
and now comcast seems to be requiring authorization rather than
just an IP-based method of allowing mail through their smtp server.

My qmail queue is full of mail that can't go out through
smtp.comcast.net, so I removed the smtproutes routing and now
most, but not all mail can get out via my IP, but of course
lots of domains (and rightly so) don't want to accept email
from my consumer IP-block.  

As I see it I've got a few options:

1. Pay for a real ISP that lets me do what I want with my 
   connection.

2. Find a smtp relaying service that can accept mail from my
   IP.  Do these exist?  I haven't found one.

3. Find out if qmail has a method of doing the authentication
   required by smtp.comcast.net.

My question for this list is directed at option 3, but I'll
take any suggestions.

Thanks!