Failed to send notification email about comments

Hello guys,

When a user comments on a post from my site, the post author should receive a notification email about the comment received. However, as an administrator I am receiving an email informing me that sending the email to the author is failing. See the reply message below:

Undelivered Mail Returned to Sender
De: MAILER-DAEMON@gateway32.websitewelcome.com	Data: Hoje 00:20

This is the mail system at host gateway32.websitewelcome.com.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<e-mail-author@hotmail.com>: host
    hotmail-com.olc.protection.outlook.com[104.47.4.33] said: 451 4.7.650 The
    mail server [192.185.145.111] has been temporarily rate limited due to IP
    reputation. For e-mail delivery information, see
    https://postmaster.live.com (S3113)
    [AM5EUR02FT016.eop-EUR02.prod.protection.outlook.com] (in reply to MAIL
    FROM command)
______________________________________________________________________
Reporting-MTA: dns; gateway32.websitewelcome.com
X-Postfix-Queue-ID: A446E7386CC
X-Postfix-Sender: rfc822; e-mail@my-site.com.br
Arrival-Date: Thu, 18 Apr 2019 19:56:09 -0500 (CDT)

Final-Recipient: rfc822; e-mail-author@hotmail.com
Original-Recipient: rfc822;e-mail-author@hotmail.com
Action: failed
Status: 4.7.650
Remote-MTA: dns; hotmail-com.olc.protection.outlook.com
Diagnostic-Code: smtp; 451 4.7.650 The mail server [192.185.145.111] has been
    temporarily rate limited due to IP reputation. For e-mail delivery
    information, see https://postmaster.live.com (S3113)
    [AM5EUR02FT016.eop-EUR02.prod.protection.outlook.com]

I did a submission test and received the email normally. But when it comes to sending e-mail to the authors of your posts notifying you of comments, I’ve noticed that the submissions are failing.

Can anyone tell me what this can be?