The addnew script in Argosoft Mail Server Pro 1.8.7.6 allows remote attackers to create arbitrary accounts, even if "Allow Creation of Accounts From the Web Interface" is disabled, via a direct HTTP POST request.
https://exchange.xforce.ibmcloud.com/vulnerabilities/20228
https://euvd.enisa.europa.eu/vulnerability/EUVD-2005-1287