I get it when the forum sends me an email when you respond to my post.
Subject: Does Blesta have a Privacy Policy?
From: "Blesta Community Forums"<forums@blesta.com>
Date: Wed, 11 Nov 2020 16:07:01 +0000
Actually to explain further, the forum sends email to my gmail account and I forward all of my gmail to another email system and that system rejects that forward with that error when it comes from blesta.com. It gets bounced back to gmail into my inbox from Mail Delivery Subsystem <mailer-daemon@googlemail.com> with subject Delivery Status Notification (Failure) with that error on it Diagnostic-Code: smtp; 550 5.7.1 Email rejected per DMARC policy for blesta.com
So I'm guessing the blesta mail server's SPF or DKIM doesn't align with the DMARC policy or something or other.
I also found this extra info in the logs if it's helpful in some way:
dsn=5.2.1, stat=failure, 5.2.1 DMARC failed