Reading Mimecast's FAQ: https://community.mimecast.com/s/article/Mimecast-SMTP-5xx-Error-Codes-573763479
Error 550 with reason "Blocked" is not listed in their FAQ. I have called Mimecast and they are not returning my call. We have a client who is getting this bounceback when sending emails through a mass email service. I have verified their SPF record is correct. They do not have a DKIM record set up. Their mass email service says to contact Mimecast. So I am stuck at the moment and hope someone has an answer for this.
X-SendGrid-QueueID: 644483390
X-SendGrid-Sender: <bounces+28313-3d0d-hill=####.com@email.bullhornmail.com>
Arrival-Date: 2020-07-21 19-51-57
Final-Recipient: rfc822; ####@####.com
Original-Recipient: rfc822; ####@####.com
Action: failed
Status:
Diagnostic-Code: 550 spamcop.mimecast.org Blocked - see https://www.spamcop.net/bl.shtml?167.89.63.60. - https://community.mimecast.com/docs/DOC-1369#550 [bZ52-d7nMLmippSyFi6_bA.us116]