The tab labeled “messages” is similar to an email inbox. IDOR uses this feature to send one-way communications to you, and this tab serves as your inbox for these communications. You cannot reply to these messages.
The tab labeled “letters” contains copies of correspondence mailed to you by IDOR. This tab is helpful if you lose or misplace a piece of correspondence. In addition, if you set up your tax preparer as a secondary or third-party user, they will have access to the correspondence without the hassle of delivery.