diff --git a/actionmailer/lib/action_mailer/deprecated_api.rb b/actionmailer/lib/action_mailer/deprecated_api.rb
index d096ea618008c04782b4f62f17be5fe0229bd7cf..19c94aee8d9dba7be85dacaceca63901deae714a 100644
--- a/actionmailer/lib/action_mailer/deprecated_api.rb
+++ b/actionmailer/lib/action_mailer/deprecated_api.rb
@@ -30,23 +30,48 @@ def attachment(params, &block)
       super # Run deprecation hooks
 
       params = { :content_type => params } if String === params
-      
-      if filename = params.delete(:filename)
-        content_disposition = "attachment; filename=\"#{File.basename(filename)}\""
+
+      if params[:filename]
+        params = normalize_file_hash(params)
       else
-        content_disposition = "attachment"
+        params = normalize_nonfile_hash(params)
       end
-      
-      params[:content] = params.delete(:data) if params[:data]
-      
-      params = { :content_disposition => content_disposition,
-                 :content_transfer_encoding => "base64" }.merge(params)
-
       part(params, &block)
     end
 
     private
     
+    def normalize_nonfile_hash(params)
+      content_disposition = "attachment;"
+      
+      mime_type = params.delete(:mime_type)
+      
+      if content_type = params.delete(:content_type)
+        content_type = "#{mime_type || content_type};"
+      end
+
+      params[:body] = params.delete(:data) if params[:data]
+      
+      { :content_type => content_type,
+        :content_disposition => content_disposition }.merge(params)
+    end
+    
+    def normalize_file_hash(params)
+      filename = File.basename(params.delete(:filename))
+      content_disposition = "attachment; filename=\"#{File.basename(filename)}\""
+      
+      mime_type = params.delete(:mime_type)
+      
+      if (content_type = params.delete(:content_type)) && (content_type !~ /filename=/)
+        content_type = "#{mime_type || content_type}; filename=\"#{filename}\""
+      end
+      
+      params[:body] = params.delete(:data) if params[:data]
+      
+      { :content_type => content_type,
+        :content_disposition => content_disposition }.merge(params)
+    end
+    
     def create_mail #:nodoc:
       m = @message
 
diff --git a/actionmailer/test/mail_service_test.rb b/actionmailer/test/mail_service_test.rb
index f83e13f16f21ac66bab45e471318b576af27052a..51d722ea0028337000707132cbcfca7c04301e5a 100644
--- a/actionmailer/test/mail_service_test.rb
+++ b/actionmailer/test/mail_service_test.rb
@@ -1036,7 +1036,7 @@ def test_decode_message_with_unknown_charset
   def test_empty_header_values_omitted
     result = TestMailer.create_unnamed_attachment(@recipient).encoded
     assert_match %r{Content-Type: application/octet-stream;}, result
-    assert_match %r{Content-Disposition: attachment[^;]}, result
+    assert_match %r{Content-Disposition: attachment;}, result
   end
 
   def test_headers_with_nonalpha_chars