diff --git a/src/java/davmail/caldav/CaldavConnection.java b/src/java/davmail/caldav/CaldavConnection.java
index 9339334e..360cb58e 100644
--- a/src/java/davmail/caldav/CaldavConnection.java
+++ b/src/java/davmail/caldav/CaldavConnection.java
@@ -7,6 +7,7 @@ import davmail.exchange.ExchangeSessionFactory;
 import davmail.tray.DavGatewayTray;
 import org.apache.commons.httpclient.HttpException;
 import org.apache.commons.httpclient.HttpStatus;
+import org.apache.commons.httpclient.auth.AuthenticationException;
 
 import javax.xml.stream.XMLInputFactory;
 import javax.xml.stream.XMLStreamConstants;
@@ -109,7 +110,11 @@ public class CaldavConnection extends AbstractConnection {
                             if (session == null) {
                                 // first check network connectivity
                                 ExchangeSessionFactory.checkConfig();
+                                try {
                                 session = ExchangeSessionFactory.getInstance(userName, password);
+                                } catch (AuthenticationException e) {
+                                     sendErr(HttpStatus.SC_UNAUTHORIZED, e.getMessage());
+                                }
                             }
                             handleRequest(command, path, headers, content);
                         }
diff --git a/src/java/davmail/exchange/ExchangeSession.java b/src/java/davmail/exchange/ExchangeSession.java
index 97579daa..168a0650 100644
--- a/src/java/davmail/exchange/ExchangeSession.java
+++ b/src/java/davmail/exchange/ExchangeSession.java
@@ -3,6 +3,7 @@ package davmail.exchange;
 import davmail.Settings;
 import davmail.http.DavGatewayHttpClientFacade;
 import org.apache.commons.httpclient.*;
+import org.apache.commons.httpclient.auth.AuthenticationException;
 import org.apache.commons.httpclient.methods.GetMethod;
 import org.apache.commons.httpclient.methods.PostMethod;
 import org.apache.commons.httpclient.methods.PutMethod;
@@ -316,8 +317,9 @@ public class ExchangeSession {
             }
             int status = method.getStatusCode();
 
-            // User may be authenticated, get various session information
-            if (status != HttpStatus.SC_OK) {
+            if (status == HttpStatus.SC_UNAUTHORIZED) {
+                throw new AuthenticationException("Authentication failed: invalid user or password");
+            } else if (status != HttpStatus.SC_OK) {
                 HttpException ex = new HttpException();
                 ex.setReasonCode(status);
                 ex.setReason(method.getStatusText());
@@ -328,9 +330,9 @@ public class ExchangeSession {
             if (queryString != null && queryString.contains("reason=2")) {
                 method.releaseConnection();
                 if (poolKey.userName != null && poolKey.userName.contains("\\")) {
-                    throw new HttpException("Authentication failed: invalid user or password");
+                    throw new AuthenticationException("Authentication failed: invalid user or password");
                 } else {
-                    throw new HttpException("Authentication failed: invalid user or password, " +
+                    throw new AuthenticationException("Authentication failed: invalid user or password, " +
                             "retry with domain\\user");
                 }
             }
@@ -349,6 +351,9 @@ public class ExchangeSession {
 
             wdr.setPath(URIUtil.getPath(inboxUrl));
 
+        } catch (AuthenticationException exc) {
+            LOGGER.error(exc.toString());
+            throw exc;
         } catch (IOException exc) {
             StringBuffer message = new StringBuffer();
             message.append("DavMail login exception: ");