It looks like I had to re-learn this the hard way, but r8.1 seems to have no way whatsoever to send voicemail to email via TLS. Every time I added and saved an entry with port 587, it's gone next time I log in. Is port 25 really the only way to send emails on these bad boys?

With that old a release, I would install an SMTP relay on the VM server, such as hMailserver or Stunnel. Configure the VMPro to send email to the SMTP relay, configure the SMTP relay to sent to email with modern security settings so that it will get through.