We reviewed the logs again and found the following:
[26-Jan-2023 13:39:20 UTC] PHP Fatal error: Uncaught Error: Call to undefined function Laminas\Mail\Header\iconv_mime_encode() in /home/[redacted]/public_html/support/include/laminas-mail/src/Header/HeaderWrap.php:157
Stack trace:
#0 /home/[redacted]/public_html/support/include/laminas-mail/src/Header/Subject.php(103): Laminas\Mail\Header\HeaderWrap::canBeEncoded('osTicket test e...')
#1 /home/[redacted]/public_html/support/include/laminas-mail/src/Message.php(344): Laminas\Mail\Header\Subject->setSubject('osTicket test e...')
#2 /home/[redacted]/public_html/support/include/class.mailer.php(349): Laminas\Mail\Message->setSubject('osTicket test e...')
#3 /home/[redacted]/public_html/support/include/class.email.php(235): osTicket\Mail\Mailer->send('khtroubleshooti...', 'osTicket test e...', '<p>KH Troublesh...', Array, Array)
#4 /home/[redacted]/public_html/support/scp/emailtest.php(38): Email->send('khtroubleshooti...', 'osTicket test e...', '<p>KH Troublesh...', NULL, Array)
#5 {main} thrown in /home/[redacted]/public_html/support/include/laminas-mail/src/Header/HeaderWrap.php on line
It appears the PHP version (8.1) was lacking iconv extension.
After installing this, a test email appears to be sent successfully, and all other operations are not functioning correctly.
Thanks for the assistance.