I have 5 domains at JustHost.com, which is also BlueHost.com. Our e-mails are being bounced by several domains, for example:

Reporting-MTA: dns; soproxy1.mail.unifiedlayer.com
X-Postfix-Queue-ID: 25AD2175A72
X-Postfix-Sender: rfc822; us@ourdomain.org
Arrival-Date: Thu, 24 Aug 2017 07:07:08 -0600 (MDT)

Final-Recipient: rfc822; them@aol.com
Original-Recipient: rfc822;them@aol.com
Action: failed
Status: 5.2.1
Remote-MTA: dns; mailin-04.mx.aol.com
Diagnostic-Code: smtp; 521 5.2.1 :  AOL will not accept delivery of this
    message.

JustHost says:

It is a known issue, you will have to try after sometime.
And if you want permanent solution for that you will have to purchase Gsuite.
​If you purchase G suite it will point to Google so your emails will work.

Duh, trying after some time is not an acceptable solution. And I can use Google myself without buying a product that should be included if the service does not work.

I am going to move all my domains to another ISP.