CiviMail throws the error
Mailing_send_test : STARTTLS failed when doing a test email. Sending results in bounces. I have a handful of CiviCRM installations running on the same server and only 4.7 installs seem affected.
Version 4.6.9 no error. Version 4.7.3+ error as described.
Does anyone know what would have caused this?
(I did recently add mysqli per the recent blog post, and I went from PHP 5.5.38 to 5.6.24 in the process. But perhaps that's unrelated.)
Edit: I use CiviSMTP.