diff --git a/apps/meteor/app/lib/server/functions/processWebhookMessage.ts b/apps/meteor/app/lib/server/functions/processWebhookMessage.js
similarity index 70%
rename from apps/meteor/app/lib/server/functions/processWebhookMessage.ts
rename to apps/meteor/app/lib/server/functions/processWebhookMessage.js
index 5671f47adf47..1e5c34b287bb 100644
--- a/apps/meteor/app/lib/server/functions/processWebhookMessage.ts
+++ b/apps/meteor/app/lib/server/functions/processWebhookMessage.js
@@ -1,4 +1,3 @@
-import type { IMessage, IUser } from '@rocket.chat/core-typings';
 import { Meteor } from 'meteor/meteor';
 import _ from 'underscore';
 
@@ -8,39 +7,9 @@ import { validateRoomMessagePermissionsAsync } from '../../../authorization/serv
 import { getRoomByNameOrIdWithOptionToJoin } from './getRoomByNameOrIdWithOptionToJoin';
 import { sendMessage } from './sendMessage';
 
-type Payload = {
-	channel?: string | string[];
-	roomId?: string | string[];
-	text?: IMessage['msg'];
-	msg?: IMessage['msg']; // overrided if text is present
-	username?: IMessage['alias'];
-	alias?: IMessage['alias']; // overrided if username is present
-	icon_emoji?: IMessage['emoji'];
-	emoji?: IMessage['emoji']; // overrided if icon_emoji is present
-	icon_url?: IMessage['avatar'];
-	avatar?: IMessage['avatar']; // overrided if icon_url is present
-	attachments?: IMessage['attachments'];
-	parseUrls?: boolean;
-	bot?: IMessage['bot'];
-	groupable?: IMessage['groupable'];
-	tmid?: IMessage['tmid'];
-};
-
-type DefaultValues = {
-	channel: string | string[];
-	alias: string;
-	avatar: string;
-	emoji: string;
-};
-
-export const processWebhookMessage = async function (
-	messageObj: Payload,
-	user: IUser & { username: Exclude<IUser['username'], undefined> },
-	defaultValues: DefaultValues = { channel: '', alias: '', avatar: '', emoji: '' },
-) {
+export const processWebhookMessage = async function (messageObj, user, defaultValues = { channel: '', alias: '', avatar: '', emoji: '' }) {
 	const sentData = [];
-
-	const channels: Array<string> = [...new Set(messageObj.channel || messageObj.roomId || defaultValues.channel)];
+	const channels = [].concat(messageObj.channel || messageObj.roomId || defaultValues.channel);
 
 	for await (const channel of channels) {
 		const channelType = channel[0];
@@ -100,7 +69,7 @@ export const processWebhookMessage = async function (
 			messageObj.attachments = undefined;
 		}
 
-		const message: Partial<IMessage> & { parseUrls?: boolean } = {
+		const message = {
 			alias: messageObj.username || messageObj.alias || defaultValues.alias,
 			msg: trim(messageObj.text || messageObj.msg || ''),
 			attachments: messageObj.attachments || [],
@@ -122,7 +91,7 @@ export const processWebhookMessage = async function (
 
 		if (Array.isArray(message.attachments)) {
 			for (let i = 0; i < message.attachments.length; i++) {
-				const attachment = message.attachments[i] as Exclude<IMessage['attachments'], undefined>[number] & { msg?: string };
+				const attachment = message.attachments[i];
 				if (attachment.msg) {
 					attachment.text = trim(attachment.msg);
 					delete attachment.msg;
diff --git a/packages/rest-typings/src/v1/chat.ts b/packages/rest-typings/src/v1/chat.ts
index ccfaa2c4a2fa..b8def106c78a 100644
--- a/packages/rest-typings/src/v1/chat.ts
+++ b/packages/rest-typings/src/v1/chat.ts
@@ -697,8 +697,8 @@ const ChatGetDeletedMessagesSchema = {
 export const isChatGetDeletedMessagesProps = ajv.compile<ChatGetDeletedMessages>(ChatGetDeletedMessagesSchema);
 
 type ChatPostMessage =
-	| { roomId: string | string[]; text?: string; alias?: string; emoji?: string; avatar?: string; attachments?: MessageAttachment[] }
-	| { channel: string | string[]; text?: string; alias?: string; emoji?: string; avatar?: string; attachments?: MessageAttachment[] };
+	| { roomId: string; text?: string; alias?: string; emoji?: string; avatar?: string; attachments?: MessageAttachment[] }
+	| { channel: string; text?: string; alias?: string; emoji?: string; avatar?: string; attachments?: MessageAttachment[] };
 
 const ChatPostMessageSchema = {
 	oneOf: [
@@ -706,15 +706,7 @@ const ChatPostMessageSchema = {
 			type: 'object',
 			properties: {
 				roomId: {
-					oneOf: [
-						{ type: 'string' },
-						{
-							type: 'array',
-							items: {
-								type: 'string',
-							},
-						},
-					],
+					type: 'string',
 				},
 				text: {
 					type: 'string',
@@ -746,16 +738,8 @@ const ChatPostMessageSchema = {
 		{
 			type: 'object',
 			properties: {
-				roomId: {
-					oneOf: [
-						{ type: 'string' },
-						{
-							type: 'array',
-							items: {
-								type: 'string',
-							},
-						},
-					],
+				channel: {
+					type: 'string',
 				},
 				text: {
 					type: 'string',