Manual talk:$wgEnableEmail

SELinux causes Mail to fail silently
If you enable email, and it's not working, you might want to check the Security Enhanced Linux (SELinux) settings in RHEL6, Scientific Linux, etc. to find out if the webserver is allowed to send email. If it's not, you'll get failures but without any helpful information on why mail is not working. httpd_can_sendmail --> off Allow Apache to send email, using -P to persist the setting across reboots: