Hello.Check out Hoats, I recommend PHP 7.2. Check the server logs, if there are errors or request blocking, then this may be the cause of the problem. Try different ways to send letters (SMTP etc).
Contact the hosting technical support service, maybe they will be able to give you a solution.

It works fine previously, only until the recent upload this had failed. Will check with my hosting provider and revert soonest on their findings and feedback.

Dear Aleksej;

Below is respond received from the hosting provider. Just to let you know this start to occur only when I start using the Beta Program. 

"Hi

Thanks for contacting us

Upon checking, it seem the error logs showing related with your script environment.

Parse error: syntax error, unexpected '?' in /home/hidangtraimmy1/public_html/res/x5engine.php on line 2426 "

Hi, i try to replace the x5engine.php file with the script generated from non beta version and it works fine. The failure only starts when generated/using the beta version. Please refer the attached files for both version. 

I recommend using the stable version.

As the project has been upgraded/created to using beta version, is there a way for me to revert to the stable version. Thanks.. really need to resolve this issue. 

Hi, Khalid Ahmad

I had the same problem after upgrading to BETA. I solved it in such a way that I deleted the mailing module and recreated it. I remembered this because in the past, I used to be similar to what happened with some other modules, and when switching from the old version to the new stable version.

I recently received beta update 2019.3.13 in which the error message has no longer shown. However the email still failed to be send with respond below. Java script is enable/activated, the email still not able to deliver. Attached screenshot for your reference. The said page https://www.hidang.com.my/feedback.html