diff --git a/src/http.ts b/src/http.ts
index b5e741be0..3f1721b5d 100644
--- a/src/http.ts
+++ b/src/http.ts
@@ -100,7 +100,8 @@ export class HttpClient implements IHttpClient {
           }
         }
       }
-      headers['Content-Type'] = 'multipart/related; type="application/xop+xml"; start="<' + start + '>"; start-info="text/xml"; boundary=' + uuidv4();
+      const boundary = uuidv4();
+      headers['Content-Type'] = 'multipart/related; type="application/xop+xml"; start="<' + start + '>"; type="text/xml"; boundary=' + boundary;
       if (action) {
         headers['Content-Type'] = headers['Content-Type'] + '; ' + action;
       }
@@ -119,7 +120,21 @@ export class HttpClient implements IHttpClient {
           'body': attachment.body,
         });
       });
-      // options.multipart = multipart;
+      options.data = `--${boundary}\r\n`;
+
+      let multipartCount = 0;
+      multipart.forEach((part) => {
+        Object.keys(part).forEach((key) => {
+          if (key !== "body") {
+            options.data += `${key}: ${part[key]}\r\n`;
+          }
+        });
+        options.data += "\r\n";
+        options.data += `${part.body}\r\n--${boundary}${
+          multipartCount === multipart.length - 1 ? "--" : ""
+        }\r\n`;
+        multipartCount++;
+      });
     } else {
       options.data = data;
     }