[SOLVED] HELP!!!!! New orders are marked as "Missing Orders" and cancelled - after migration to another host

I need some urgent help with a site that I recently moved to a different hosting company.
The site was restored perfectly but when a customer places an order and pay through PayFast the client receives the receipt but the orders are sent straight to "Missing Orders" and the status set to "Cancelled". When I try and change the status of the order to "Processed" a popu that reads "error" appears.

I contacted my hosting company and they replied with the following:
We have checked the server logs and could not find any server-wide issues. However, we could find PHP compatibility errors while performing saving the orders in opencart. You may refer to the error log attached.
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PHP Fatal error: Uncaught Exception: Error: EHLO not accepted from server! in /home/suppobas/public_html/opencart/system/library/mail/smtp.php:121
Stack trace:
#0 /home/suppobas/public_html/opencart/system/library/mail.php(142): Mail\Smtp->send()
#1 /home/suppobas/public_html/opencart/catalog/controller/mail/order.php(275): Mail->send()
#2 /home/suppobas/public_html/opencart/catalog/controller/mail/order.php(34): ControllerMailOrder->add(Array, '15', '', '')
#3 /home/suppobas/public_html/storage/modification/system/engine/action.php(79): ControllerMailOrder->index('checkout/order/...', Array)
#4 /home/suppobas/public_html/storage/modification/system/engine/event.php(67): Action->execute(Object(Registry), Array)
#5 /home/suppobas/public_html/storage/modification/system/engine/loader.php(237): Event->trigger('model/checkout/...', Array)
#6 /home/suppobas/public_html/opencart/system/engine/proxy.php(47): Loader->{closure}(Array, Array)
#7 /home/suppobas/public_html/opencart/catalog/controller/api/order.php(688): Proxy->__call('a in /home/suppobas/public_html/opencart/system/library/mail/smtp.php on line 121

The order e-mail is triggering a Fatal PHP error, which is stopping the order from completing. This is why it shows up in Missing Orders and doesn't complete properly.

Your SMTP settings in System > Settings > Mail tab are likely wrong. Double-check those and fix them.

Thank you so much for your reply. You were right, I changed the Mail Engine from SMTP to Mail and all is fine now.
Such a simple solution....