diff --git a/src/java/davmail/AbstractConnection.java b/src/java/davmail/AbstractConnection.java
index 749d6691..298be7b3 100644
--- a/src/java/davmail/AbstractConnection.java
+++ b/src/java/davmail/AbstractConnection.java
@@ -163,7 +163,6 @@ public class AbstractConnection extends Thread {
         } catch (IOException e2) {
             DavGatewayTray.warn("Exception closing client socket", e2);
         }
-        ExchangeSessionFactory.close(session);
     }
 
     protected String base64Encode(String value) {
diff --git a/src/java/davmail/exchange/ExchangeSession.java b/src/java/davmail/exchange/ExchangeSession.java
index d2ebf1ce..62b184ea 100644
--- a/src/java/davmail/exchange/ExchangeSession.java
+++ b/src/java/davmail/exchange/ExchangeSession.java
@@ -86,13 +86,6 @@ public class ExchangeSession {
         PRIORITIES.put("2", "1 (Highest)");
     }
 
-    /**
-     * Date parser/formatter from Exchange format
-     */
-    private final SimpleDateFormat dateFormatter;
-    private final SimpleDateFormat dateParser;
-
-
     /**
      * Various standard mail boxes Urls
      */
@@ -127,17 +120,15 @@ public class ExchangeSession {
      */
     ExchangeSession(ExchangeSessionFactory.PoolKey poolKey) {
         this.poolKey = poolKey;
-        // SimpleDateFormat are not thread safe, need to create one instance for
-        // each session
-        dateFormatter = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
-        dateFormatter.setTimeZone(GMT_TIMEZONE);
-
-        dateParser = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS");
-        dateParser.setTimeZone(GMT_TIMEZONE);
-
         LOGGER.debug("Session " + this + " created");
     }
 
+    protected String formatDate(Date date) {
+        SimpleDateFormat dateFormatter = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
+        dateFormatter.setTimeZone(GMT_TIMEZONE);
+        return dateFormatter.format(date);
+    }
+
     public boolean isExpired() {
         boolean isExpired = false;
         try {
@@ -727,7 +718,7 @@ public class ExchangeSession {
         String searchRequest = "Select \"DAV:uid\"" +
                 "                FROM Scope('SHALLOW TRAVERSAL OF \"" + folderUrl + "\"')\n" +
                 "                WHERE \"DAV:isfolder\" = False\n" +
-                "                   AND \"DAV:getlastmodified\" < '" + dateFormatter.format(cal.getTime()) + "'\n";
+                "                   AND \"DAV:getlastmodified\" < '" + formatDate(cal.getTime()) + "'\n";
         Enumeration folderEnum = DavGatewayHttpClientFacade.executeSearchMethod(
                 httpClient, URIUtil.encodePath(folderUrl), searchRequest);
 
@@ -1196,7 +1187,7 @@ public class ExchangeSession {
         if (caldavPastDelay != Integer.MAX_VALUE) {
             Calendar cal = Calendar.getInstance();
             cal.add(Calendar.DAY_OF_MONTH, -caldavPastDelay);
-            dateCondition = "                AND \"urn:schemas:calendar:dtstart\" > '" + dateFormatter.format(cal.getTime()) + "'\n";
+            dateCondition = "                AND \"urn:schemas:calendar:dtstart\" > '" + formatDate(cal.getTime()) + "'\n";
         }
 
         String searchQuery = "Select \"DAV:getetag\"" +
diff --git a/src/java/davmail/exchange/ExchangeSessionFactory.java b/src/java/davmail/exchange/ExchangeSessionFactory.java
index 3f5660d0..c2031468 100644
--- a/src/java/davmail/exchange/ExchangeSessionFactory.java
+++ b/src/java/davmail/exchange/ExchangeSessionFactory.java
@@ -18,7 +18,7 @@ import java.util.*;
  */
 public final class ExchangeSessionFactory {
     private static final Object LOCK = new Object();
-    private static final Map<PoolKey, ExchangeSessionStack> poolMap = new HashMap<PoolKey, ExchangeSessionStack>();
+    private static final Map<PoolKey, ExchangeSession> poolMap = new HashMap<PoolKey, ExchangeSession>();
 
     static class PoolKey {
         public final String url;
@@ -46,34 +46,6 @@ public final class ExchangeSessionFactory {
         }
     }
 
-    static class ExchangeSessionStack extends Stack<ExchangeSession> {
-        // 15 minutes expire delay
-        protected static final long EXPIRE_DELAY = 1000 * 60 * 15;
-        protected long timestamp = System.currentTimeMillis();
-
-        @Override
-        public ExchangeSession pop() throws EmptyStackException {
-            timestamp = System.currentTimeMillis();
-            return super.pop();
-        }
-
-        @Override
-        public ExchangeSession push(ExchangeSession session) {
-            timestamp = System.currentTimeMillis();
-            return super.push(session);
-        }
-
-        public boolean isExpired() {
-            return (System.currentTimeMillis() - timestamp) > EXPIRE_DELAY;
-        }
-
-        public void clean() {
-            while (!isEmpty()) {
-                pop();
-            }
-        }
-    }
-
     private ExchangeSessionFactory() {
     }
 
@@ -90,18 +62,21 @@ public final class ExchangeSessionFactory {
             String baseUrl = Settings.getProperty("davmail.url");
             PoolKey poolKey = new PoolKey(baseUrl, userName, password);
 
-            ExchangeSession session = null;
+            ExchangeSession session;
             synchronized (LOCK) {
-                Stack<ExchangeSession> sessionStack = poolMap.get(poolKey);
-                if (sessionStack != null && !sessionStack.isEmpty()) {
-                    session = sessionStack.pop();
-                    ExchangeSession.LOGGER.debug("Got session " + session + " from pool");
-                }
+                session = poolMap.get(poolKey);
+            }
+            if (session != null) {
+                ExchangeSession.LOGGER.debug("Got session " + session + " from cache");
             }
 
             if (session != null && session.isExpired()) {
                 ExchangeSession.LOGGER.debug("Session " + session + " expired");
                 session = null;
+                // expired session, remove from cache
+                synchronized (LOCK) {
+                    poolMap.remove(poolKey);
+                }
             }
 
             if (session == null) {
@@ -109,6 +84,10 @@ public final class ExchangeSessionFactory {
                 session.login();
                 ExchangeSession.LOGGER.debug("Created new session: " + session);
             }
+            // successfull login, put session in cache
+            synchronized (LOCK) {
+                poolMap.put(poolKey, session);
+            }
             return session;
         } catch (IOException e) {
             if (checkNetwork()) {
@@ -119,41 +98,6 @@ public final class ExchangeSessionFactory {
         }
     }
 
-    /**
-     * Close (or pool) session.
-     *
-     * @param session exchange session
-     */
-    public static void close(ExchangeSession session) {
-        synchronized (LOCK) {
-            if (session != null) {
-                PoolKey poolKey = session.getPoolKey();
-                ExchangeSessionStack sessionStack = poolMap.get(poolKey);
-                if (sessionStack == null) {
-                    sessionStack = new ExchangeSessionStack();
-                    poolMap.put(poolKey, sessionStack);
-                }
-                // keep httpClient
-                sessionStack.push(session);
-                ExchangeSession.LOGGER.debug("Pooled session: " + session);
-            }
-
-            // clean pool
-            List<PoolKey> toDeleteKeys = new ArrayList<PoolKey>();
-            for (Map.Entry<PoolKey, ExchangeSessionStack> entry : poolMap.entrySet()) {
-                if (entry.getValue().isExpired()) {
-                    ExchangeSession.LOGGER.debug("Session pool for " + entry.getKey().userName + " expired");
-                    entry.getValue().clean();
-                    toDeleteKeys.add(entry.getKey());
-                }
-            }
-            for (PoolKey toDeleteKey : toDeleteKeys) {
-                poolMap.remove(toDeleteKey);
-            }
-        }
-    }
-
-
     public static void checkConfig() throws IOException {
         String url = Settings.getProperty("davmail.url");
         HttpClient httpClient = DavGatewayHttpClientFacade.getInstance();
diff --git a/src/java/davmail/ldap/LdapConnection.java b/src/java/davmail/ldap/LdapConnection.java
index 214df4f3..65fae398 100644
--- a/src/java/davmail/ldap/LdapConnection.java
+++ b/src/java/davmail/ldap/LdapConnection.java
@@ -413,7 +413,6 @@ public class LdapConnection extends AbstractConnection {
             } else if (requestOperation == LDAP_REQ_UNBIND) {
                 DavGatewayTray.debug("LDAP_REQ_UNBIND " + currentMessageId);
                 if (session != null) {
-                    ExchangeSessionFactory.close(session);
                     session = null;
                 }
             } else if (requestOperation == LDAP_REQ_SEARCH) {