diff --git a/lib/imap-flow.js b/lib/imap-flow.js
index e08cd5e..fc20828 100644
--- a/lib/imap-flow.js
+++ b/lib/imap-flow.js
@@ -1992,6 +1992,7 @@ class ImapFlow extends EventEmitter {
      * @property {String} [keyword] Matches messages that have the custom flag set
      * @property {String} [unKeyword] Matches messages that do not have the custom flag set
      * @property {Object.<string, Boolean|String>} [header] Matches messages with header key set if value is `true` (**NB!** not supported by all servers) or messages where header partially matches a string value
+     * @property {SearchObject} [not] A {@link SearchObject} object. It must not match.
      * @property {SearchObject[]} [or] An array of 2 or more {@link SearchObject} objects. At least on of these must match
      */
 
diff --git a/lib/search-compiler.js b/lib/search-compiler.js
index 1ddf17c..f4a3b22 100644
--- a/lib/search-compiler.js
+++ b/lib/search-compiler.js
@@ -190,6 +190,19 @@ module.exports.searchCompiler = (connection, query) => {
                     }
                     break;
 
+                case 'NOT':
+                    {   
+                        if (!params[term]) {
+                            break;
+                        }
+
+                        if (typeof params[term] === 'object') {
+                            attributes.push({ type: 'ATOM', value: 'NOT' });
+                            walk(params[term]);
+                        }
+                    }
+                    break;
+                    
                 case 'OR':
                     {
                         if (!params[term] || !Array.isArray(params[term]) || !params[term].length) {