For any unsolvable problem with the standard email sending function, you have the option of implementing your own as follows:
1. Rename the qa-external-example directory to qa-external.
2. In qa-config.php, set QA_EXTERNAL_EMAILER to true.
3. Write the qa_send_email() function in qa-external-emailer.php.
For step 3, this can be as simple as using PHP's mail() function, or an email sending library that you know works under your server configuration.