diff --git a/src/components/MailboxThread.vue b/src/components/MailboxThread.vue
index bf75ab543a..95aaa40025 100644
--- a/src/components/MailboxThread.vue
+++ b/src/components/MailboxThread.vue
@@ -220,7 +220,7 @@ import {
 	priorityImportantQuery,
 	priorityOtherQuery,
 } from '../util/priorityInbox.js'
-import { detect, html } from '../util/text.js'
+import { detect, toHtml, toPlain } from '../util/text.js'
 
 const START_MAILBOX_DEBOUNCE = 5 * 1000
 
@@ -535,6 +535,9 @@ export default {
 				if (this.$route.params.accountId !== 0 && this.$route.params.accountId !== '0') {
 					accountId = parseInt(this.$route.params.accountId, 10)
 				}
+
+				const body = detect(this.$route.query.body ?? '')
+
 				this.mainStore.startComposerSession({
 					data: {
 						accountId,
@@ -542,7 +545,9 @@ export default {
 						cc: this.stringToRecipients(this.$route.query.cc),
 						bcc: this.stringToRecipients(this.$route.query.bcc),
 						subject: this.$route.query.subject || '',
-						body: this.$route.query.body ? detect(this.$route.query.body) : html(''),
+						isHtml: body.format === 'html',
+						bodyHtml: toHtml(body).value,
+						bodyPlain: toPlain(body).value,
 					},
 				})
 			}
diff --git a/src/store/mainStore/actions.js b/src/store/mainStore/actions.js
index 27388e9b9c..83059563be 100644
--- a/src/store/mainStore/actions.js
+++ b/src/store/mainStore/actions.js
@@ -115,6 +115,15 @@ import {
 } from '../constants.js'
 import useOutboxStore from '../outboxStore.js'
 
+/**
+ * @todo Type definition for ComposerSessionData is incomplete
+ *
+ * @typedef {object} ComposerSessionData
+ * @property {boolean} isHtml whether this is a html message
+ * @property {string} bodyHtml the body as html
+ * @property {string} bodyPlain the body as plain text
+ */
+
 const sliceToPage = slice(0, PAGE_SIZE)
 
 const findIndividualMailboxes = curry((getMailboxes, specialRole) => pipe(
@@ -1936,7 +1945,7 @@ export default function mainStoreActions() {
 		 *
 		 * @param {object} payload Data for the new message
 		 * @param payload.type
-		 * @param payload.data
+		 * @param {ComposerSessionData} payload.data
 		 * @param payload.forwardedMessages
 		 * @param payload.originalSendAt
 		 * @param payload.smartReply
diff --git a/src/util/text.js b/src/util/text.js
index 8e4a692537..4c6a02a97c 100644
--- a/src/util/text.js
+++ b/src/util/text.js
@@ -51,6 +51,10 @@ export const plain = wrap('plain')
  */
 export const html = wrap('html')
 
+/**
+ * @param {string} str
+ * @return {Text}
+ */
 export function detect(str) {
 	if (!isString(str)) {
 		// Fall back to a hopefully sane default