Problem with Opencart emails

I have a problem to send emails from my website, everything is working but after few days it does not work anymore. Each time I have to reboot the server to make it work again, I cannot do that all the time, I need a clear solution. I thought it may be linked to updates of cpanel for EA or something else but I am not sure.
I do use openssl, apache and php 5.6. It seems the problem is linked to the certificate and openssl. I use the Opencart Framework 2.0.1.1.

I tried to add this trick when creating the socket client:
$streamContext = stream_context_create([
'ssl' => [
'verify_peer' => false,
'verify_peer_name' => false
]
]);

See forum.codeigniter.com/archive/index.php?thread-590.html for the thing I did follow.
However, this does not seem to solve the problem since the password does not get accepted for the smtp account.

I do use tls://smtp-relay.gmail.com with port 587.

I would appreciate if I get a solution to this problem as soon as possible because I am losing money right now, my customers cannot log or even contact us.