Use a default password hash

cmd/mailfull/command/domainadd.go

@@ -61,7 +61,7 @@ func (c *DomainAddCommand) Run(args []string) int {
 		return 1
 	}
 
-	user, err := mailfull.NewUser("postmaster", "", nil)
+	user, err := mailfull.NewUser("postmaster", mailfull.NeverMatchHashedPassword, nil)
 	if err != nil {
 		fmt.Fprintf(c.UI.ErrorWriter, "[ERR] %v\n", err)
 		return 1

const.go

@@ -18,3 +18,6 @@ const (
 	FileNameDbForwards     = "forwards"
 	FileNameDbPasswords    = "vpasswd"
 )
+
+// NeverMatchHashedPassword is hash string that is never match with any password.
+const NeverMatchHashedPassword = "{SSHA}!!"