diff --git a/app/assets/javascripts/app/controllers/_integration/slack.coffee b/app/assets/javascripts/app/controllers/_integration/slack.coffee
index 8ecfd085d..a579aa548 100644
--- a/app/assets/javascripts/app/controllers/_integration/slack.coffee
+++ b/app/assets/javascripts/app/controllers/_integration/slack.coffee
@@ -27,7 +27,7 @@ class Index extends App.ControllerIntegrationBase
       { name: 'webhook',  display: 'Webhook',  tag: 'input', type: 'url', limit: 200, 'null': false, placeholder: 'https://hooks.slack.com/services/...' },
       { name: 'username', display: 'Username', tag: 'input', type: 'text', limit: 100, 'null': false, placeholder: 'username' },
       { name: 'channel',  display: 'Channel',  tag: 'input', type: 'text', limit: 100, 'null': true, placeholder: '#channel' },
-      { name: 'icon_url',  display: 'Icon Url',  tag: 'input', type: 'url', limit: 200, 'null': true, placeholder: 'http://example.com/logo.png' },
+      { name: 'icon_url',  display: 'Icon Url',  tag: 'input', type: 'url', limit: 200, 'null': true, placeholder: 'https://example.com/logo.png' },
     ]
 
     settings = []
diff --git a/app/models/transaction/slack.rb b/app/models/transaction/slack.rb
index 7a6bb9752..7cf0d29fd 100644
--- a/app/models/transaction/slack.rb
+++ b/app/models/transaction/slack.rb
@@ -46,16 +46,20 @@ backend.perform
     # get user based notification template
     # if create, send create message / block update messages
     template = nil
+    sent_value = nil
     if @item[:type] == 'create'
       template = 'ticket_create'
     elsif @item[:type] == 'update'
       template = 'ticket_update'
     elsif @item[:type] == 'reminder_reached'
       template = 'ticket_reminder_reached'
+      sent_value = ticket.pending_time
     elsif @item[:type] == 'escalation'
       template = 'ticket_escalation'
+      sent_value = ticket.escalation_time
     elsif @item[:type] == 'escalation_warning'
       template = 'ticket_escalation_warning'
+      sent_value = ticket.escalation_time
     else
       raise "unknown type for notification #{@item[:type]}"
     end
@@ -88,6 +92,24 @@ backend.perform
 
     config['items'].each {|item|
 
+      # check if reminder_reached/escalation/escalation_warning is already sent today
+      md5_webhook = Digest::MD5.hexdigest(@item['webhook'])
+      cache_key = "slack::backend::#{@item[:type]}::#{md5_webhook}"
+      if sent_value
+        value = Cache.get(cache_key)
+        if value == sent_value
+          Rails.logger.debug "did not send webhook, already sent (#{@item[:type]}/#{ticket.id}/#{@item['webhook']})"
+          next
+        end
+        Cache.write(
+          cache_key,
+          sent_value,
+          {
+            expires_in: 24.hours
+          },
+        )
+      end
+
       # check action
       if item['types'].class == Array
         hit = false
@@ -119,7 +141,7 @@ backend.perform
         logo_url = item['logo_url']
       end
 
-      Rails.logger.debug "sent webhook (#{@item[:type]}/#{ticket.id}/#{item['webhook']})"
+      Rails.logger.debug "sent webhook (#{@item[:type]}/#{ticket.id}/#{@item['webhook']})"
 
       notifier = Slack::Notifier.new(
         item['webhook'],
@@ -142,10 +164,13 @@ backend.perform
                                attachments: [attachment]
       end
       if !result.success?
-        Rails.logger.error "Unable to post webhook: #{item['webhook']}: #{result.inspect}"
+        if sent_value
+          Cache.delete(cache_key)
+        end
+        Rails.logger.error "Unable to post webhook: #{@item['webhook']}: #{result.inspect}"
         next
       end
-      Rails.logger.debug "sent webhook (#{@item[:type]}/#{ticket.id}/#{item['webhook']})"
+      Rails.logger.debug "sent webhook (#{@item[:type]}/#{ticket.id}/#{@item['webhook']})"
     }
 
   end
diff --git a/test/integration/slack_test.rb b/test/integration/slack_test.rb
index ac000bd96..a9fd98ba2 100644
--- a/test/integration/slack_test.rb
+++ b/test/integration/slack_test.rb
@@ -34,7 +34,7 @@ class SlackTest < ActiveSupport::TestCase
     items = [
       {
         group_ids: [slack_group.id],
-        types: %w(create update),
+        types: %w(create update reminder_reached),
         webhook: webhook,
         channel: channel,
         username: 'zammad bot',
@@ -72,7 +72,7 @@ class SlackTest < ActiveSupport::TestCase
     Delayed::Worker.new.work_off
 
     # check if message exists
-    assert_not(slack_check(channel, hash))
+    assert_equal(0, slack_check(channel, hash))
 
     ticket1.state = Ticket::State.find_by(name: 'open')
     ticket1.save
@@ -81,7 +81,7 @@ class SlackTest < ActiveSupport::TestCase
     Delayed::Worker.new.work_off
 
     # check if message exists
-    assert_not(slack_check(channel, hash))
+    assert_equal(0, slack_check(channel, hash))
 
     # case 2
     hash = hash_gen
@@ -110,7 +110,7 @@ class SlackTest < ActiveSupport::TestCase
     Delayed::Worker.new.work_off
 
     # check if message exists
-    assert(slack_check(channel, hash))
+    assert_equal(1, slack_check(channel, hash))
 
     hash = hash_gen
     text = "#{rand_word}... #{hash}"
@@ -122,7 +122,33 @@ class SlackTest < ActiveSupport::TestCase
     Delayed::Worker.new.work_off
 
     # check if message exists
-    assert(slack_check(channel, hash))
+    assert_equal(1, slack_check(channel, hash))
+
+    ticket2.state = Ticket::State.find_by(name: 'pending reminder')
+    ticket2.pending_time = Time.zone.now - 2.days
+    ticket2.save
+
+    Observer::Transaction.commit
+    Delayed::Worker.new.work_off
+
+    # check if message exists
+    assert_equal(2, slack_check(channel, hash))
+
+    Ticket.process_pending
+
+    Observer::Transaction.commit
+    Delayed::Worker.new.work_off
+
+    # check if message exists
+    assert_equal(3, slack_check(channel, hash))
+
+    Ticket.process_pending
+
+    Observer::Transaction.commit
+    Delayed::Worker.new.work_off
+
+    # check if message exists
+    assert_equal(3, slack_check(channel, hash))
 
     items = [
       {
@@ -165,7 +191,7 @@ class SlackTest < ActiveSupport::TestCase
     Delayed::Worker.new.work_off
 
     # check if message exists
-    assert_not(slack_check(channel, hash))
+    assert_equal(0, slack_check(channel, hash))
 
     ticket3.state = Ticket::State.find_by(name: 'open')
     ticket3.save
@@ -174,7 +200,7 @@ class SlackTest < ActiveSupport::TestCase
     Delayed::Worker.new.work_off
 
     # check if message exists
-    assert_not(slack_check(channel, hash))
+    assert_equal(0, slack_check(channel, hash))
 
     # case 4
     hash = hash_gen
@@ -203,7 +229,7 @@ class SlackTest < ActiveSupport::TestCase
     Delayed::Worker.new.work_off
 
     # check if message exists
-    assert(slack_check(channel, hash))
+    assert_equal(1, slack_check(channel, hash))
 
     hash = hash_gen
     text = "#{rand_word}... #{hash}"
@@ -215,7 +241,7 @@ class SlackTest < ActiveSupport::TestCase
     Delayed::Worker.new.work_off
 
     # check if message exists
-    assert_not(slack_check(channel, hash))
+    assert_equal(0, slack_check(channel, hash))
 
   end
 
@@ -271,15 +297,15 @@ class SlackTest < ActiveSupport::TestCase
     if !channel_history['messages']
       raise "ERROR: No history messages for channel #{channel_name}/#{channel_id}"
     end
+    message_count = 0
     channel_history['messages'].each {|message|
       next if !message['text']
       if message['text'] =~ /#{search_for}/i
-        p "SUCCESS: message with #{search_for} found!"
-        return true
+        message_count += 1
+        p "SUCCESS: message with #{search_for} found #{message_count} time(s)!"
       end
     }
-    #raise "ERROR: No such message containing #{search_for} in history of channel #{channel_name}/#{channel_id}"
-    false
+    message_count
   end
 
 end