I can trigger the error if I create a new email address and set the option "Identical to remote mailbox" in the SMTP authentication, then I get the error message "Resource user different".
So that I can save the dialogue, I change the authentication to no authentication and when I then change the authentication back to "Identical to remote mailbox", I get the 500 error.
[30-Jun-2024 20:23:36 UTC] PHP Fatal error: Uncaught Error: Call to undefined method osTicket\Mail\BasicAuthCredentials::getAccessToken() in C:\inetpub\wwwroot\osTicketdeu\include\class.email.php:561
Stack trace:
#0 C:\inetpub\wwwroot\osTicketdeu\include\class.email.php(495): EmailAccount->getAccessToken()
#1 C:\inetpub\wwwroot\osTicketdeu\include\class.email.php(1353): EmailAccount->checkStrictMatching()
#2 C:\inetpub\wwwroot\osTicketdeu\include\class.email.php(1381): SmtpAccount->setInfo()
#3 C:\inetpub\wwwroot\osTicketdeu\include\class.email.php(328): SmtpAccount->update()
#4 C:\inetpub\wwwroot\osTicketdeu\scp\emails.php(35): Email->update()
#5 {main}
thrown in C:\inetpub\wwwroot\osTicketdeu\include\class.email.php on line 561
osTicketdeu\include\class.email.php on line 561