I upgraded from Moodle 2.6 to Moodle 2.9.5+, from Ubuntu 12 to 14, as well as going to PHP 5.6 and Apache 2.4.7. After the upgrade, I can no longer email via Admin > Bulk user actions or via forum posts. I didn't change any Moodle email settings during the upgrade to my knowledge. I tested sendmail via Ubuntu command line prompt and it tests fine. I get Moodle cron emails just fine. The SMTP security setting is turned off. There was an additional mailbox configuration requiring adding mailbox name and email name, but it appears that is for incoming mail only, which is disabled.
I turned on email debugging but I don't get any debug information when using email bulk send or posting to a forum.
I did make a slight change to mod/forum/lib.php but I don't believe that is causing any php errors, and it worked before the upgrade, and I don't think it would affect bulk user action messaging.
My mail.log file doesn't appear to have forum posts in it...
PHP error log is clean.
I'm getting a ton of errors in syslog "May 31 10:01:26 moodle23 console-kit-daemon[1633]: GLib-CRITICAL: Source ID 64094 was not found when attempting to remove it" which I need to look into. I don't think it's related.
Any suggestions for how to go about troubleshooting this issue would be appreciated!