diff --git a/config.go b/config.go
index 14d36bf..8e4894d 100644
--- a/config.go
+++ b/config.go
@@ -43,6 +43,10 @@ var (
 	versionInfo       = flag.Bool("version", false, "Show version information")
 )
 
+func localAuthRequired() bool {
+	return *allowedUsers != ""
+}
+
 
 func setupAllowedNetworks() {
 	for _, netstr := range splitstr(*allowedNetsStr, ' ') {
diff --git a/main.go b/main.go
index c48deff..ba77aa5 100644
--- a/main.go
+++ b/main.go
@@ -81,7 +81,7 @@ func addrAllowed(addr string, allowedAddrs []string) bool {
 
 func senderChecker(peer smtpd.Peer, addr string) error {
 	// check sender address from auth file if user is authenticated
-	if *allowedUsers != "" && peer.Username != "" {
+	if localAuthRequired() && peer.Username != "" {
 		user, err := AuthFetch(peer.Username)
 		if err != nil {
 			// Shouldn't happen: authChecker already validated username+password
@@ -276,7 +276,7 @@ func main() {
 		Debug("starting smtprelay")
 
 	// Load allowed users file
-	if *allowedUsers != "" {
+	if localAuthRequired() {
 		err := AuthLoadFile(*allowedUsers)
 		if err != nil {
 			log.WithField("file", *allowedUsers).
@@ -300,7 +300,7 @@ func main() {
 			Handler:           mailHandler,
 		}
 
-		if *allowedUsers != "" {
+		if localAuthRequired() {
 			server.Authenticator = authChecker
 		}