Comcast & Greylisting

I recently noticed that Comcast and greylisting don't seem to get 
along....  They appear to be originating mail from the following IPs:

	+-----------------+
	| relay_ip        |
	+-----------------+
	| 204.127.192.83  |
	| 204.127.192.84  |
	| 204.127.200.81  |
	| 204.127.200.85  |
	| 204.127.225.91  |
	| 204.127.225.93  |
	| 204.127.225.94  |
	| 206.18.177.53   |
	| 206.18.177.54   |
	| 216.148.227.153 |
	| 216.148.227.154 |
	+-----------------+

Which resolve to the following names:
	alnrmhc11.comcast.net
	alnrmhc13.comcast.net
	alnrmhc14.comcast.net
	rwcrmhc13.comcast.net
	rwcrmhc14.comcast.net
	sccrmhc11.comcast.net
	sccrmhc15.comcast.net

Which is interesting because when you look closer there appear to be 
multiple IPs bound to each of their outbound servers and those IPs 
are on completely different subnets (which is where greylisting is 
getting broken, I assume):

	alnrmhc11.comcast.net   A       204.127.225.91
	alnrmhc11.comcast.net   A       206.18.177.51

Does anybody have some secret sauce to deal with this?  I'm loathe to 
just blanket whitelist these IPs.....

Brian Ross
IT Engineer, Sr. - Messaging Services
Postmaster - QUALCOMM, Inc.