diff --git a/src/calibre/library/server/content.py b/src/calibre/library/server/content.py
index 6953deff5f..11a22bd859 100644
--- a/src/calibre/library/server/content.py
+++ b/src/calibre/library/server/content.py
@@ -20,7 +20,7 @@ from calibre.utils.filenames import ascii_filename
 from calibre.ebooks.metadata.opf2 import metadata_to_opf
 
 plugboard_content_server_value = 'content_server'
-plugboard_content_server_formats = ['epub']
+plugboard_content_server_formats = ['epub', 'mobi', 'azw3']
 
 class CSSortKeyGenerator(SortKeyGenerator):
 
@@ -224,13 +224,11 @@ class ContentServer(object):
             mt = 'application/octet-stream'
         cherrypy.response.headers['Content-Type'] = mt
 
-        if format == 'EPUB':
-            # Get the original metadata
-
-            # Get any EPUB plugboards for the content server
+        if format.lower() in plugboard_content_server_formats:
+            # Get any plugboards for the content server
             plugboards = self.db.prefs.get('plugboards', {})
             cpb = find_plugboard(plugboard_content_server_value,
-                                 'epub', plugboards)
+                                 format.lower(), plugboards)
             if cpb:
                 # Transform the metadata via the plugboard
                 newmi = mi.deepcopy_metadata()