Internal server error 500 at checkout (/index.php?route=extension/payment/cod/confirm )

Hey everyone!
I got this error everytime when i try to checkout:
Failed to load resource: the server responded with a status of 500 (Internal Server Error) /index.php?route=extension/payment/cod/confirm
Also this my error.log:
#0 /home/csiguhu/public_html/system/library/mail.php(142): Mail\Smtp->send()
#1 /home/csiguhu/public_html/catalog/controller/mail/order.php(275): Mail->send()
#2 /home/csiguhu/public_html/catalog/controller/mail/order.php(34): ControllerMailOrder->add(Array, '1', '', '')
#3 /home/csiguhu/public_html/system/engine/action.php(79): ControllerMailOrder->index('checkout/order/...', Array)
#4 /home/csiguhu/public_html/system/engine/event.php(62): Action->execute(Object(Registry), Array)
#5 /home/csiguhu/public_html/system/engine/loader.php(229): Event->trigger('model/checkout/...', Array)
#6 /home/csiguhu/public_html/system/engine/proxy.php(47): Loader->{closure}(Array, Array)
#7 /home/csiguhu/public_html/catalog/controller/extension/payment/cod.php(13): Proxy->__call('addOrderHistory', Array)
#8 /home/csiguhu/public_html/system/engine/action.php(79): ControllerExtensionPaymentCod in /home/csiguhu/public_html/system/library/mail/smtp.php on line 205

I tried to change my STMP email settings i tried with my hosting mail and with gmail also.
I cant figure it it out what could be the problem.
Thanks for your help in forward.

Hi. As a new forum user, please read the most recent forum rules. No OC version posted. The issue originates from the admin - > systems - > settings - > edit settings - > Mail tab. Ensure the mail form is properly configured. If you are not sure of your email configuration settings on what they should be, contact your host. In addition, you can try the email extensions from the Marketplace.