diff --git a/calendar/experiments/calendar/parent/ext-calendar-provider.js b/calendar/experiments/calendar/parent/ext-calendar-provider.js
index b1d2a68..a5f6e3d 100644
--- a/calendar/experiments/calendar/parent/ext-calendar-provider.js
+++ b/calendar/experiments/calendar/parent/ext-calendar-provider.js
@@ -131,42 +131,17 @@ class ExtCalendarProvider extends cal.provider.BaseClass {
   scheme = "mailto";
 
   async sendItems(aRecipients, aItipItem) {
-    let responseMethod = aItipItem.responseMethod;
     let transport = super.getProperty("itip.transport").wrappedJSObject;
     let { subject, body } = transport._prepareItems(aItipItem);
-    let serializer = Cc["@mozilla.org/calendar/ics-serializer;1"].createInstance(Ci.calIIcsSerializer);
-    let itemList = aItipItem.getItemList();
-    serializer.addItems(itemList, itemList.length);
-    let methodProp = cal.getIcsService().createIcalProperty("METHOD");
-    methodProp.value = responseMethod;
-    serializer.addProperty(methodProp);
-    let icsText = serializer.serializeToString();
-    let boundary = Array.from({ length: 24 }, () => Math.floor(Math.random() * 16).toString(16)).join("");
-    let headers = new Map();
-    headers.set("Date", [new Date()]);
-    headers.set("Subject", [subject]);
-    headers.set("To", aRecipients.map(attendee => ({ name: attendee.commonName, email: attendee.id.replace(/^mailto:/, "")})));
-    headers.set("Content-Type", ["multipart/mixed; boundary=\"" + boundary + "\""]);
-    let mimeContent = jsmime.headeremitter.emitStructuredHeaders(headers, { hardMargin: 800 }) + "\r\n";
-    mimeContent += "--" + boundary + "\r\n";
-    mimeContent += "Content-Type: text/plain; charset=UTF-8\r\n\r\n";
-    mimeContent += body + "\r\n";
-    mimeContent += "--" + boundary + "\r\n";
-    mimeContent += "Content-Type: text/calendar; method=" + responseMethod + "; charset=UTF-8\r\nContent-Transfer-Encoding: 8BIT\r\n\r\n";
-    mimeContent += icsText;
-    mimeContent += "--" + boundary + "\r\n";
-    mimeContent += "Content-Type: application/ics; name=\"invite.ics\"\r\nContent-Disposition: attachment; filename=\"invite.ics\"\r\nContent-Transfer-Encoding: 8BIT\r\n\r\n";
-    mimeContent += icsText;
-    mimeContent += "--" + boundary + "--\r\n";
-    let recipients = aRecipients.map(attendee => attendee.id.replace(/^mailto:/, ""));
-    let responses = await this.extension.emit("calendar.provider.onBeforeSend", this, { responseMethod, recipients, subject, body, icsText, mimeContent });
+    let recipients = aRecipients.map(attendee => ({ name: attendee.commonName, email: attendee.id.replace(/^mailto:/, "")}));
+    let responses = await this.extension.emit("calendar.provider.onBeforeSend", this, aItipItem, { recipients, subject, body });
     for (let response of responses) {
       if (response === true) {
         return;
       }
       if (Array.isArray(response?.recipients)) {
         for (let recipient of response.recipients) {
-          aRecipients = aRecipients.filter(attendee => attendee.id.replace(/^mailto:/, "") != recipient);
+          aRecipients = aRecipients.filter(attendee => attendee.id.replace(/^mailto:/, "") != recipient.email);
         }
       }
     }
@@ -509,8 +484,41 @@ this.calendar_provider = class extends ExtensionAPI {
           onBeforeSend: new EventManager({
             context,
             name: "calendar.provider.onBeforeSend",
-            register: fire => {
-              let listener = (event, calendar, content) => {
+            register: (fire, options) => {
+              let listener = (event, calendar, itipItem, content) => {
+                content.responseMethod = itipItem.responseMethod;
+                if (["ics", "mime"].includes(options?.returnFormat)) {
+                  let serializer = Cc["@mozilla.org/calendar/ics-serializer;1"].createInstance(Ci.calIIcsSerializer);
+                  serializer.addItems(itipItem.getItemList());
+                  let methodProp = cal.getIcsService().createIcalProperty("METHOD");
+                  methodProp.value = content.responseMethod;
+                  serializer.addProperty(methodProp);
+                  let icsText = serializer.serializeToString();
+                  if (options.returnFormat == "mime") {
+                    let boundary = Array.from({ length: 24 }, () => Math.floor(Math.random() * 16).toString(16)).join("");
+                    let headers = new Map();
+                    headers.set("Date", [new Date()]);
+                    headers.set("Subject", [content.subject]);
+                    headers.set("To", content.recipients);
+                    headers.set("Content-Type", ["multipart/mixed; boundary=\"" + boundary + "\""]);
+                    let mimeContent = jsmime.headeremitter.emitStructuredHeaders(headers, { hardMargin: 800 }) + "\r\n";
+                    mimeContent += "--" + boundary + "\r\n";
+                    mimeContent += "Content-Type: text/plain; charset=UTF-8\r\n\r\n";
+                    mimeContent += content.body + "\r\n";
+                    mimeContent += "--" + boundary + "\r\n";
+                    mimeContent += "Content-Type: text/calendar; method=" + content.responseMethod + "; charset=UTF-8\r\nContent-Transfer-Encoding: 8BIT\r\n\r\n";
+                    mimeContent += icsText;
+                    mimeContent += "--" + boundary + "\r\n";
+                    mimeContent += "Content-Type: application/ics; name=\"invite.ics\"\r\nContent-Disposition: attachment; filename=\"invite.ics\"\r\nContent-Transfer-Encoding: 8BIT\r\n\r\n";
+                    mimeContent += icsText;
+                    mimeContent += "--" + boundary + "--\r\n";
+                    content.mimeContent = mimeContent;
+                  } else {
+                    content.icsText = icsText;
+                  }
+                } else {
+                  content.items = itipItem.getItemList().map(item => convertItem(item, options, context.extension));
+                }
                 return fire.async(convertCalendar(context.extension, calendar), content);
               };
 
diff --git a/calendar/experiments/calendar/schema/calendar-provider.json b/calendar/experiments/calendar/schema/calendar-provider.json
index 70e3659..20ac293 100644
--- a/calendar/experiments/calendar/schema/calendar-provider.json
+++ b/calendar/experiments/calendar/schema/calendar-provider.json
@@ -93,15 +93,38 @@
         "parameters": [
           { "name": "calendar", "$ref": "calendar.calendars.Calendar" },
           {
-            "name": "mimeContent",
+            "name": "content",
             "type": "object",
             "properties": {
               "responseMethod": { "type": "string" },
-              "recipients": { "type": "array", "items": { "type": "string" } },
+              "recipients": {
+                "type": "array",
+                "items": {
+                  "type": "object",
+                  "properties": {
+                    "name": { "type": "string" },
+                    "email": { "type": "string" }
+                  }
+                }
+              },
               "subject": { "type": "string" },
               "body": { "type": "string" },
-              "icsText": { "type": "string" },
-              "mimeContent": { "type": "string" }
+              "items": { "type": "array", "items": { "$ref": "calendar.items.CalendarItem" }, "optional": true },
+              "icsText": { "type": "string", "optional": true },
+              "mimeContent": { "type": "string", "optional": true }
+            }
+          }
+        ],
+        "extraParameters": [
+          {
+            "type": "object",
+            "optional": true,
+            "properties": {
+              "returnFormat": {
+                "optional": true,
+                "type": "string",
+                "enum": ["ical", "jcal", "ics", "mime"]
+              }
             }
           }
         ]