We use a product/service called ExactTarget.com. They provide the means to send to these large lists, while providing statistics and other handy tools. They have strict rules governing their use and they do not tolerate clients using their services to send spam. They want to remain on the good side of the very narrow line between legitimate marketing email and spam.
Some of our customers ISPs or even their internal IT departments refuse to open up their server level filters to us, leaving us and our contact at that company with no reasonable option. Basically they are out of luck.
I've seen this kind of spam filtering before and while it's quite effective at blocking junk email, it has a high rate of false-positives. In other words, lots of legitimate email gets filtered out as well. Personally I feel this is much too drastic, especially when the email administrator is unwilling to give his/her users an flexibility. A few of our customers' ISPs were quite willing to open up our emails to our client. Others almost laughed in their faces and said, "In your dreams!" Email Dictators!
What we use here, where I work (I use it at home too), is a much more personalized approch, where the end user can make the determination of whether the email is junk or not. It's a free open-source product called "SpamBayes". You can get it from SourceForge. It's a great filter that 'learns' through a little training what is spam and what is 'ham' (good email). Through statistical analysis it is quite successful at moving junk into the junk folder and it also has a nice 'suspects' folder for those emails that it's not quite sure about.
Since implementing SpamBayes the users here have been a LOT happier and I very rarely hear any problems about junk mail now. If you're a home user or work user, take a look at this product. If you have a lot of issues with junk mail, you'll like this product and solution a lot more than letting your ISP screen everything.