diff --git a/lib/griddler/mailgun/adapter.rb b/lib/griddler/mailgun/adapter.rb
index de98a25..7e54936 100644
--- a/lib/griddler/mailgun/adapter.rb
+++ b/lib/griddler/mailgun/adapter.rb
@@ -4,7 +4,7 @@ class Adapter
       attr_reader :params
 
       def initialize(params)
-        @params = params
+        @params = params.transform_keys(&:downcase)
       end
 
       def self.normalize_params(params)
@@ -16,7 +16,7 @@ def normalize_params
         {
           to: to_recipients,
           cc: cc_recipients,
-          bcc: Array.wrap(param_or_header(:Bcc)),
+          bcc: Array.wrap(param_or_header(:bcc)),
           from: determine_sender,
           subject: params[:subject],
           text: params['body-plain'],
@@ -34,23 +34,23 @@ def normalize_params
     private
 
       def determine_sender
-        sender = param_or_header(:From)
+        sender = param_or_header(:from)
         sender ||= params[:sender]
       end
 
       def to_recipients
-        to_emails = param_or_header(:To)
+        to_emails = param_or_header(:to)
         to_emails ||= params[:recipient]
         to_emails.split(',').map(&:strip)
       end
 
       def cc_recipients
-        cc = param_or_header(:Cc) || ''
+        cc = param_or_header(:cc) || ""
         cc.split(',').map(&:strip)
       end
 
       def headers
-        @headers ||= extract_headers
+        @headers ||= extract_headers.transform_keys(&:downcase)
       end
 
       def extract_headers
diff --git a/spec/griddler/mailgun/adapter_spec.rb b/spec/griddler/mailgun/adapter_spec.rb
index bf78fb9..57d188b 100644
--- a/spec/griddler/mailgun/adapter_spec.rb
+++ b/spec/griddler/mailgun/adapter_spec.rb
@@ -78,6 +78,14 @@
     expect(normalized_params[:to]).to eq ['johndoe@example.com']
   end
 
+  it "handles downcased params" do
+    downcased = {
+      to: "John Doe <johndoe@example.com>"
+    }
+    normalized_params = Griddler::Mailgun::Adapter.normalize_params(downcased)
+    expect(normalized_params[:to]).to eq ["John Doe <johndoe@example.com>"]
+  end
+
   it 'handles message-headers' do
     params = default_params.merge(
       'message-headers' => '[["NotCc", "emily@example.mailgun.org"], ["Reply-To", "mail2@example.mailgun.org"]]'
@@ -174,7 +182,6 @@ def default_params
         "To"=>"John Doe <johndoe@example.com>, Jane Doe <janedoe@example.com>",
         "body-html"=>"<div dir=\"ltr\">And attachments. Two of them. An image and a text file.</div>\r\n",
         "body-plain"=>"And attachments. Two of them. An image and a text file.\r\n",
-        "from"=>"Jon Snow <jon@example.com>",
         "recipient"=>"johndoe@example.com",
         "sender"=>"jon@example.com",
         "stripped-html"=>"<div dir=\"ltr\">And attachments. Two of them. An image and a text file.</div>\r\n",