diff --git a/config/default.js b/config/default.js
index 8a00e5d..2178cbe 100644
--- a/config/default.js
+++ b/config/default.js
@@ -132,6 +132,13 @@ module.exports = {
             },
             disableInterfaces: ['forwarder'], // do not bounce messages from this interface
             sendingZone: 'bounces',
+
+            // send a warning email about delayed delivery
+            delayEmail: {
+                enabled: true,
+                after: 3 * 3600 * 1000
+            },
+
             zoneConfig: {
                 // specify zone specific bounce options
                 myzonename: {
diff --git a/lib/mail-queue.js b/lib/mail-queue.js
index 5f6866b..f6d304e 100644
--- a/lib/mail-queue.js
+++ b/lib/mail-queue.js
@@ -745,31 +745,38 @@ class MailQueue {
      *
      * @param {Object} delivery Message object
      * @param {Number} ttl TTL in ms. Once this time is over the message is reinserted to queue
-     * @param {Number} responseData SMTP response or description
+     * @param {Object} responseData SMTP response or description
      * @param {Function} callback Run once the message is removed from active queue
      */
     deferDelivery(delivery, ttl, responseData, callback) {
         // add metainfo about postponing the delivery
-        delivery._deferred = delivery._deferred || {
-            first: Date.now(),
-            count: 0
-        };
-        delivery._deferred.count++;
-        delivery._deferred.last = Date.now();
-        delivery._deferred.next = Date.now() + ttl;
-        delivery._deferred.response = responseData.response;
-        delivery._deferred.log = responseData.log || delivery._deferred.log;
-        delivery.queued = new Date(Math.max(delivery._deferred.next, Date.now()));
-        delivery.locked = false;
+
+        const now = Date.now();
 
         let updates = {
             $set: {
-                _deferred: delivery._deferred,
-                queued: delivery.queued,
+                '_deferred.last': now,
+                '_deferred.next': now + ttl,
+                queued: new Date(now + ttl),
                 locked: false
+            },
+            $inc: {
+                '_deferred.count': 1
             }
         };
 
+        if (!delivery._deferred) {
+            updates.$set['_deferred.first'] = now;
+        }
+
+        if (responseData.response) {
+            updates.$set['_deferred.response'] = responseData.response;
+        }
+
+        if (responseData.log) {
+            updates.$set['_deferred.log'] = responseData.log;
+        }
+
         if (responseData.updates && typeof responseData.updates === 'object') {
             Object.keys(responseData.updates).forEach(key => {
                 if (key.charAt(0) === '$') {
@@ -777,7 +784,7 @@ class MailQueue {
                         return; // not allowed
                     }
                     // $inc etc.
-                    updates[key] = responseData.updates[key];
+                    updates[key] = Object.assign(updates[key] || {}, responseData.updates[key]);
                     return;
                 }
                 if (!updates.$set.hasOwnProperty(key)) {
@@ -787,13 +794,16 @@ class MailQueue {
         }
 
         let collection = this.mongodb.collection(this.options.collection);
-        collection.updateOne(
+        collection.findOneAndUpdate(
             {
                 id: delivery.id,
                 seq: delivery.seq
             },
             updates,
-            err => {
+            {
+                returnOriginal: true
+            },
+            (err, item) => {
                 if (err) {
                     return callback(err);
                 }
@@ -802,6 +812,34 @@ class MailQueue {
                 log.verbose('Queue', '%s.%s UNLOCK (key="%s")', delivery.id, delivery.seq, delivery._lock);
                 this.locks.release(delivery._lock);
 
+                if (item && item.value) {
+                    let firstCheck = item.value._deferred && item.value._deferred.first;
+                    let prevLastCheck = item.value._deferred && item.value._deferred.last;
+                    let lastCheck = now;
+
+                    if (firstCheck && prevLastCheck) {
+                        return plugins.handler.runHooks(
+                            'queue:delayed',
+                            [
+                                delivery,
+                                responseData,
+                                {
+                                    first: firstCheck,
+                                    prev: prevLastCheck,
+                                    last: lastCheck
+                                }
+                            ],
+                            err => {
+                                if (err) {
+                                    log.error('Queue', '%s.%s queue:delayed %s', delivery.id, delivery.seq, err.message);
+                                }
+
+                                return callback(null, true);
+                            }
+                        );
+                    }
+                }
+
                 return callback(null, true);
             }
         );
diff --git a/lib/queue-server.js b/lib/queue-server.js
index 1624f36..c4ca6fb 100644
--- a/lib/queue-server.js
+++ b/lib/queue-server.js
@@ -180,7 +180,7 @@ class QueueServer {
                             );
                         });
                     }
-                    case 'DEFER':
+                    case 'DEFER': {
                         if (!client.zone) {
                             return client.send({
                                 req: data.req,
@@ -190,6 +190,7 @@ class QueueServer {
                         deliveryStatusCounter.inc({
                             status: 'deferred'
                         });
+
                         return this.deferDelivery(client.zone, client.id, data, (err, response) => {
                             if (!client) {
                                 // client already errored or closed
@@ -206,11 +207,12 @@ class QueueServer {
                                 response
                             });
                         });
+                    }
 
                     case 'BOUNCE':
                         {
                             bounceCounter.inc();
-                            let bounce = data;
+                            const bounce = data;
                             bounce.headers = new Headers(bounce.headers || []);
                             plugins.handler.runHooks(
                                 'queue:bounce',
diff --git a/plugins/core/email-bounce.js b/plugins/core/email-bounce.js
index 0559884..3fc82aa 100644
--- a/plugins/core/email-bounce.js
+++ b/plugins/core/email-bounce.js
@@ -4,7 +4,7 @@ const os = require('os');
 const MimeNode = require('nodemailer/lib/mime-node');
 
 module.exports.title = 'Email Bounce Notification';
-module.exports.init = function(app, done) {
+module.exports.init = function (app, done) {
     // generate a multipart/report DSN failure response
     function generateBounceMessage(bounce) {
         let headers = bounce.headers;
@@ -72,10 +72,7 @@ Status: 5.0.0
 `
             );
 
-        rootNode
-            .createChild('text/rfc822-headers')
-            .setHeader('Content-Description', 'Undelivered Message Headers')
-            .setContent(headers.build());
+        rootNode.createChild('text/rfc822-headers').setHeader('Content-Description', 'Undelivered Message Headers').setContent(headers.build());
 
         return rootNode;
     }
@@ -132,5 +129,29 @@ Status: 5.0.0
         });
     });
 
+    app.addHook('queue:delayed', async (delivery, bounce, options) => {
+        if (!app.config.delayEmail || !app.config.delayEmail.enabled) {
+            return;
+        }
+
+        // check if past required time
+        let prevDiff = options.prev - options.first;
+        let curDiff = options.last - options.first;
+        if (prevDiff > app.config.delayEmail.after || curDiff < app.config.delayEmail.after) {
+            return;
+        }
+
+        app.logger.info(
+            'Bounce',
+            'Should send a delay email %s',
+            JSON.stringify({
+                id: delivery.id,
+                seq: delivery.seq,
+                recipient: delivery.recipient,
+                response: bounce.response
+            })
+        );
+    });
+
     done();
 };