Hmm, I'm testing a php script that mails a user for password recovery, and in the about 20 instances I've used it to test sending mail, 1 mail got to a mailbox.
It's sending from a valid email address I've set up that's only for sending out these mails, and no one else has used it but me for these tests.
On this note, a second email arrived, and when I checked the header, it spent at least a hour traveling between multiple dreamhost servers before being sent out to gmail.
But at least it arrived. All the others haven't been so lucky.
Someone really needs to check into this.