diff --git a/app/models/channel/email_build.rb b/app/models/channel/email_build.rb
index b01182cbf..67e6eae51 100644
--- a/app/models/channel/email_build.rb
+++ b/app/models/channel/email_build.rb
@@ -105,13 +105,13 @@ module Channel::EmailBuild
     attr[:attachments]&.each do |attachment|
       if attachment.class == Hash
         attachment['content-id'] = nil
-        mail.attachments[ attachment[:filename] ] = attachment
+        mail.attachments[attachment[:filename]] = attachment
       else
         next if attachment.preferences['Content-ID'].present?
         filename = attachment.filename
         encoded_filename = Mail::Encodings.decode_encode filename, :encode
         disposition = attachment.preferences['Content-Disposition'] || 'attachment'
-        content_type = attachment.preferences['Content-Type'] || 'application/octet-stream'
+        content_type = attachment.preferences['Content-Type'] || attachment.preferences['Mime-Type'] || 'application/octet-stream'
         mail.attachments[attachment.filename] = {
           content_disposition: "#{disposition}; filename=\"#{encoded_filename}\"",
           content_type: "#{content_type}; filename=\"#{encoded_filename}\"",
diff --git a/test/unit/email_build_test.rb b/test/unit/email_build_test.rb
index cf6585e4d..71d850ab4 100644
--- a/test/unit/email_build_test.rb
+++ b/test/unit/email_build_test.rb
@@ -49,8 +49,8 @@ class EmailBuildTest < ActiveSupport::TestCase
         {
           'Mime-Type' => 'image/png',
           :content      => 'xxx',
-          :filename     => 'somename.png',
-        },
+          :filename     => 'somename.png'
+        }
       ],
     )
 
@@ -103,8 +103,8 @@ class EmailBuildTest < ActiveSupport::TestCase
         {
           'Mime-Type' => 'image/png',
           :content      => 'xxx',
-          :filename     => 'somename.png',
-        },
+          :filename     => 'somename.png'
+        }
       ],
     )
 
@@ -114,6 +114,7 @@ class EmailBuildTest < ActiveSupport::TestCase
 >'
     assert_equal(should, mail.text_part.body.to_s)
     assert_nil(mail.html_part)
+    assert_equal('image/png; filename=somename.png', mail.attachments[0].content_type)
 
     parser = Channel::EmailParser.new
     data = parser.parse(mail.to_s)
@@ -137,6 +138,88 @@ class EmailBuildTest < ActiveSupport::TestCase
     end
   end
 
+  test 'plain email + attachment check 2' do
+    ticket1 = Ticket.create!(
+      title: 'some article helper test1',
+      group: Group.lookup(name: 'Users'),
+      customer_id: 2,
+      state: Ticket::State.lookup(name: 'new'),
+      priority: Ticket::Priority.lookup(name: '2 normal'),
+      updated_by_id: 1,
+      created_by_id: 1,
+    )
+    assert(ticket1, 'ticket created')
+
+    # create inbound article #1
+    article1 = Ticket::Article.create!(
+      ticket_id: ticket1.id,
+      from: 'some_sender@example.com',
+      to: 'some_recipient@example.com',
+      subject: 'some subject',
+      message_id: 'some@id',
+      content_type: 'text/html',
+      body: 'some message article helper test1 <div><img style="width: 85.5px; height: 49.5px" src="cid:15.274327094.140938@zammad.example.com">asdasd<img src="cid:15.274327094.140939@zammad.example.com"><br>',
+      internal: false,
+      sender: Ticket::Article::Sender.find_by(name: 'Customer'),
+      type: Ticket::Article::Type.find_by(name: 'email'),
+      updated_by_id: 1,
+      created_by_id: 1,
+    )
+
+    store1 = Store.add(
+      object: 'Ticket::Article',
+      o_id: article1.id,
+      data: 'content_file1_normally_should_be_an_ics_calendar_file',
+      filename: 'schedule.ics',
+      preferences: {
+        'Mime-Type' => 'text/calendar'
+      },
+      created_by_id: 1,
+    )
+
+    text = '> Welcome!
+>
+> Thank you for installing Zammad. äöüß
+>'
+    mail = Channel::EmailBuild.build(
+      from: 'sender@example.com',
+      to: 'recipient@example.com',
+      body: text,
+      attachments: [
+        store1
+      ],
+    )
+
+    should = '> Welcome!
+>
+> Thank you for installing Zammad. äöüß
+>'
+    assert_equal(should, mail.text_part.body.to_s)
+    assert_nil(mail.html_part)
+    assert_equal('text/calendar; filename=schedule.ics', mail.attachments[0].content_type)
+
+    parser = Channel::EmailParser.new
+    data = parser.parse(mail.to_s)
+
+    # check body
+    assert_equal(should, data[:body])
+
+    # check count of attachments, 2
+    assert_equal(1, data[:attachments].length)
+
+    # check attachments
+    data[:attachments]&.each do |attachment|
+      if attachment[:filename] == 'schedule.ics'
+        assert(attachment[:preferences]['Content-ID'])
+        assert_nil(attachment[:preferences]['content-alternative'])
+        assert_equal('text/calendar', attachment[:preferences]['Mime-Type'])
+        assert_equal('UTF-8', attachment[:preferences]['Charset'])
+      else
+        assert(false, "invalid attachment, should not be there, #{attachment.inspect}")
+      end
+    end
+  end
+
   test 'plain email + without attachment check' do
     text = '> Welcome!
 >