diff --git a/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Constants.cs b/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Constants.cs
index b45f9ef..8e16718 100644
--- a/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Constants.cs
+++ b/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Constants.cs
@@ -102,8 +102,16 @@ namespace Acacia
 
         public const string DATE_ISO_8601 = "yyyyMMddTHHmmssZ";
 
+        /// <summary>
+        /// Default period for synchronisation tasks
+        /// </summary>
         public static readonly TimeSpan ZPUSH_SYNC_DEFAULT_PERIOD = new TimeSpan(1, 0, 0);
 
+        /// <summary>
+        /// Default period during which synchronisation tasks will not be executed again.
+        /// </summary>
+        public static readonly TimeSpan ZPUSH_SYNC_DEFAULT_PERIOD_THROTTLE = new TimeSpan(0, 15, 0);
+
         #region Registry
 
         public const string PLUGIN_REGISTRY_BASE = "Software\\" + PRODUCT_PREFIX + "\\" + PRODUCT_NAME;
diff --git a/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Features/DebugSupport/DebugInfo.cs b/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Features/DebugSupport/DebugInfo.cs
index e6ddead..dc0244f 100644
--- a/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Features/DebugSupport/DebugInfo.cs
+++ b/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Features/DebugSupport/DebugInfo.cs
@@ -194,6 +194,16 @@ namespace Acacia.Features.DebugSupport
         {
             get { return ThisAddIn.Instance.Watcher.Sync.Period; }
         }
+        [DebugCategory(DebugCategory.Misc)]
+        public TimeSpan ZPushSyncPeriodThrottle
+        {
+            get { return ThisAddIn.Instance.Watcher.Sync.PeriodThrottle; }
+        }
+        [DebugCategory(DebugCategory.Misc)]
+        public DateTime ZPushSyncLast
+        {
+            get { return ThisAddIn.Instance.Watcher.Sync.LastSyncTime; }
+        }
 
         [DebugCategory(DebugCategory.Misc)]
         public string Build
diff --git a/src/AcaciaZPushPlugin/AcaciaZPushPlugin/GlobalOptions.cs b/src/AcaciaZPushPlugin/AcaciaZPushPlugin/GlobalOptions.cs
index 72d9fc4..7d7e9d2 100644
--- a/src/AcaciaZPushPlugin/AcaciaZPushPlugin/GlobalOptions.cs
+++ b/src/AcaciaZPushPlugin/AcaciaZPushPlugin/GlobalOptions.cs
@@ -90,6 +90,14 @@ namespace Acacia
         }
         private static readonly TimeSpanOption ZPUSH_SYNC_PERIOD = new TimeSpanOption("ZPushSyncPeriod", Constants.ZPUSH_SYNC_DEFAULT_PERIOD);
 
+        [AcaciaOption("Sets the interval during which ZPush synchronization tasks will be not executed to prevent overloading the server.")]
+        public TimeSpan ZPushSync_PeriodThrottle
+        {
+            get { return GetOption(null, ZPUSH_SYNC_PERIOD_THROTTLE); }
+            set { SetOption(null, ZPUSH_SYNC_PERIOD_THROTTLE, value); }
+        }
+        private static readonly TimeSpanOption ZPUSH_SYNC_PERIOD_THROTTLE = new TimeSpanOption("ZPushSyncPeriodThrottle", Constants.ZPUSH_SYNC_DEFAULT_PERIOD_THROTTLE);
+
         [AcaciaOption("Disables the release of COM objects. This generally leads to resource leaks and should " +
                       "only be disabled for debug purposes.")]
         public bool COMRelease
diff --git a/src/AcaciaZPushPlugin/AcaciaZPushPlugin/ZPush/ZPushSync.cs b/src/AcaciaZPushPlugin/AcaciaZPushPlugin/ZPush/ZPushSync.cs
index abed17b..179126c 100644
--- a/src/AcaciaZPushPlugin/AcaciaZPushPlugin/ZPush/ZPushSync.cs
+++ b/src/AcaciaZPushPlugin/AcaciaZPushPlugin/ZPush/ZPushSync.cs
@@ -1,4 +1,4 @@
-/// Copyright 2016 Kopano b.v.
+/// Copyright 2017 Kopano b.v.
 /// 
 /// This program is free software: you can redistribute it and/or modify
 /// it under the terms of the GNU Affero General Public License, version 3,
@@ -28,7 +28,7 @@ using System.Windows.Forms;
 namespace Acacia.ZPush
 {
     /// <summary>
-    /// Helper for synchronising state with ZPush servers
+    /// Helper for periodically synchronising state with ZPush servers
     /// </summary>
     public class ZPushSync : DisposableWrapper
     {
@@ -85,6 +85,8 @@ namespace Acacia.ZPush
 
         public readonly bool Enabled;
         public readonly TimeSpan Period;
+        public readonly TimeSpan PeriodThrottle;
+        public DateTime LastSyncTime;
 
         public ZPushSync(ZPushWatcher watcher, IAddIn addIn)
         {
@@ -93,6 +95,9 @@ namespace Acacia.ZPush
             Period = GlobalOptions.INSTANCE.ZPushSync_Period;
             if (Period.Ticks == 0)
                 Period = Constants.ZPUSH_SYNC_DEFAULT_PERIOD;
+            PeriodThrottle = GlobalOptions.INSTANCE.ZPushSync_PeriodThrottle;
+            if (PeriodThrottle.Ticks == 0)
+                PeriodThrottle = Constants.ZPUSH_SYNC_DEFAULT_PERIOD_THROTTLE;
 
             // Set up a timer and events if enabled
             if (Enabled)
@@ -174,13 +179,24 @@ namespace Acacia.ZPush
         #region Task execution
 
         /// <summary>
-        /// Executes the tasks for all known ZPush accounts
+        /// Executes the tasks for all known ZPush accounts. Only executed if enough time has passed since the last check.
         /// </summary>
-        private void ExecuteTasks()
+        private void PossiblyExecuteTasks()
         {
+            // Don't contact the network if Outlook is offline
             if (ThisAddIn.Instance.IsOffline)
                 return;
 
+            // Check for time
+            DateTime now = DateTime.Now;
+            if (LastSyncTime != null && now.Subtract(LastSyncTime) < PeriodThrottle)
+            {
+                // Back off
+                return;
+            }
+            LastSyncTime = now;
+
+            // Execute tasks for all accounts
             foreach (ZPushAccount account in _watcher.Accounts.GetAccounts())
                 ExecuteTasks(account);
         }
@@ -191,6 +207,11 @@ namespace Acacia.ZPush
         /// </summary>
         private void ExecuteTasks(ZPushAccount account)
         {
+            // Don't contact the network if Outlook is offline
+            if (ThisAddIn.Instance.IsOffline)
+                return;
+
+            // Execute the tasks for the account
             foreach (SyncTask task in _tasks)
             {
                 Tasks.Task(task.GetInstance(account));
@@ -202,7 +223,7 @@ namespace Acacia.ZPush
         /// </summary>
         private void _timer_Tick(object sender, EventArgs e)
         {
-            ExecuteTasks();
+            PossiblyExecuteTasks();
         }
 
         /// <summary>
@@ -225,7 +246,7 @@ namespace Acacia.ZPush
             if (_started)
             {
                 // Explicit sync, run tasks
-                ExecuteTasks();
+                PossiblyExecuteTasks();
             }
         }