+
+ * ldap poppassd - http://works.agni.com/ldap-poppassd.html
+ poppass server for LDAP
+
+ * yppoppassd - http://cns.georgetown.edu/~ric/software/yppoppassd/
+ poppass server for NIS/YP
+
+ * kpoppassd - http://kpoppassd.sourceforge.net/
+ poppass server for Kerberos
+
+ * Mercury32 poppassd - http://www.pmail.com/