diff --git a/lib/filter-handler.js b/lib/filter-handler.js
index f423b03d..05c29947 100644
--- a/lib/filter-handler.js
+++ b/lib/filter-handler.js
@@ -697,7 +697,6 @@ class FilterHandler {
 
         try {
             let { data } = await this.addMessage(messageOpts);
-
             if (data) {
                 filterResults.push({
                     mailbox: data.mailbox && data.mailbox.toString(),
@@ -711,7 +710,14 @@ class FilterHandler {
                         userData,
                         response: 'Message stored as ' + data.id.toString(),
                         filterResults,
-                        attachments: (maildata && maildata.attachments) || []
+                        attachments: [].concat((maildata && maildata.attachments) || []).map(att => {
+                            let binaryHash = prepared.mimeTree?.attachmentMap?.[att.id];
+                            let resp = Object.assign({}, att); // cheap copy
+                            if (binaryHash) {
+                                resp.encodedSha256 = binaryHash.toString('base64');
+                            }
+                            return resp;
+                        })
                     },
                     prepared:
                         (!isEncrypted && {