'ssl://smtp.gmail.com': (13) Permission denied in cacti

In this case you have to check SELINUX on your system whether active or not.
If it enabled, just disabled

# vi /etc/selinux/config

SELINUX=enforcing (as)

SELINUX=disabled

:wq!

#reboot

or

/usr/sbin/setsebool httpd_can_network_connect=1

reboot