The best solution is to get whitelisted with the big boys.
Follow all their rules, for example:
- only send mails out to people who have verified their email
- have a system in place to capture bounces and unverify them
- make sure your unsubscribe links work perfectly
etc...
Of the big guys, only Hotmail is a major pain to deal with because they are near impossible to get ahold of. Once done though, your mail shoudl be going through great
A lot of programs don't do this because they want to mail their members as often as possible and to as many as possible to get more signups, but they feel the hurt when they are marked as spammers
