diff --git a/lib/filter-handler.js b/lib/filter-handler.js
index ebdc50be..0a6d6290 100644
--- a/lib/filter-handler.js
+++ b/lib/filter-handler.js
@@ -766,27 +766,39 @@ async function checkFilter(filterData, prepared, maildata) {
         for (let j = prepared.headers.length - 1; j >= 0; j--) {
             let header = prepared.headers[j];
             let key = header.key;
+
             switch (key) {
                 case 'cc':
-                    if (!headerFilters.get('cc')) {
-                        // match cc against to query
+                case 'delivered-to':
+                    if (!headerFilters.get(key)) {
+                        // match against "to" query
                         key = 'to';
                     }
                     break;
+
+                case 'sender':
+                    if (!headerFilters.get(key)) {
+                        // match against "from" query
+                        key = 'from';
+                    }
+                    break;
             }
+
             if (headerFilters.has(key)) {
                 let check = headerFilters.get(key);
-                let value = (header.value || '').toString();
+                // value should already be lower case though
+                let value = (header.value || '').toString().toLowerCase();
 
                 if (check.isRegex) {
                     if (check.test(value)) {
                         headerMatches.add(key);
                     }
-                } else if (value === check || value.indexOf(check) >= 0) {
+                } else if (value.indexOf(check) >= 0) {
                     headerMatches.add(key);
                 }
             }
         }
+
         if (headerMatches.size < headerFilters.size) {
             // not enough matches
             return false;
diff --git a/lib/message-handler.js b/lib/message-handler.js
index b30b18fa..87cc976e 100644
--- a/lib/message-handler.js
+++ b/lib/message-handler.js
@@ -15,7 +15,7 @@ const openpgp = require('openpgp');
 const parseDate = require('../imap-core/lib/parse-date');
 
 // index only the following headers for SEARCH
-const INDEXED_HEADERS = ['to', 'cc', 'subject', 'from', 'sender', 'reply-to', 'message-id', 'thread-index', 'list-id'];
+const INDEXED_HEADERS = ['to', 'cc', 'subject', 'from', 'sender', 'reply-to', 'message-id', 'thread-index', 'list-id', 'delivered-to'];
 
 openpgp.config.commentstring = 'Plaintext message encrypted by WildDuck Mail Server';