Announcement List labeled as SPAM

About half of my list (mainly gmail and AOL users) is reporting that my Announcement List emails aren’t getting to them. Turns out they just go straight into their spam folder.

The list confirmation emails get through without a hitch.

but the actual e-newsletters (being sent through dreamhosts’s announcement list) get labeled as spam. If i can’t get an email to my list, then how can i tell them to make my email “safe” to their filters?