I'd say get your own dedicated host with your own IP address, and use normal outgoing mail. (I use a colocated Xserve G5 with Postfix, which is a great system.)
As long as your SMTP server is reasonably secure (you can run simple blacklist tests on it from various sites), you shouldn't get caught by IP-based spam filters, and then it's just a question of whether your content looks spammy to your recipients' mail systems. That's unrelated to how you're delivering the email, so it's the same problem no matter what you're using to send.
As long as your SMTP server is reasonably secure (you can run simple blacklist tests on it from various sites), you shouldn't get caught by IP-based spam filters, and then it's just a question of whether your content looks spammy to your recipients' mail systems. That's unrelated to how you're delivering the email, so it's the same problem no matter what you're using to send.