Hi Webdados, I agree patch core is not the solution, of course.
consider that
class-phpmailer.php contemplates SMTPOptions that Plugins shoud set
I wrote [...I suggest To author to add an option "verify_peer" true/false to plugin to override PHP 5.6 default...]
I take a look of plugin code to do this
I hope a new version of plugin relased soon
HTH
Alessandro