Thank you for getting back to me. This is very helpful information.
I have relayed this back to my hosting provider and they are looking in to it.
With that aside, would you still recommend I upload the 'newer' version of the WA_Email.php file to my server once this issue is corrected with my hosting provider? The current version on the server is v1.15 and my local file is v1.20. I have also noticed the PHPMailer.php file (attached) is different to my local file. I assume I should also upload this too?