Canvas makes it easy to reply to messages from other users in your Inbox.
If your recipient list contains more than 100 users, your message will automatically be sent as individual messages to each user. As the sender, you will also be included in the total recipient count.
If you want to reply to a submission comment, you can reply using submission comments in your Inbox or directly from your assignment or quiz.
1. In Global Navigation, click the Inbox link.
2. Click the conversation you want to respond to . Click the Reply icon in the message header, or hover over the timestamp and click the Reply icon within the message . You can also click the Reply  or Reply All  icon in the toolbar.
Note: If there is more than one recipient, you can reply-all to the conversation and everyone included will see your reply.
Reply to Message_Inbox [View Image]
3. Type your reply in the message field. You can attach a file or media using the icons in the bottom left-and corner.
4. When you are ready, click the Send button.