It appears that some years ago someone quietly removed port 465 and 587 from the reduced exit policy at https://trac.torproject.org/projects/tor/wiki/doc/ReducedExitPolicy without an explanation.
I've added them back in, since these ports should only be used for user-authenticated SMTP, and not spam. Has anyone experienced any abuse from these ports that involved non-authenticated mail/spam?
Otherwise, it seems that exit operators who were using the reduced exit policy should consider updating their polices to include these ports.