Misconfigured PTR record?

I have an office 365 hosted email account which has sent an email to a cPanel hosted email address.

I’ve received this error:

How to Fix It
The recipient’s email server at worksm8.com performed a security check against your message and the check failed. To fix this, forward this non-delivery report (NDR) to your email admin.

More Info for Email Admins
Status code: 550 5.7.363

It appears that the recipient’s email server at worksm8.com performed a reverse DNS (rDNS) lookup security check to verify that the IP address the message is coming from is associated with the sending domain, and the lookup failed. It appears that the pointer (PTR) record for chieftechofficer.co.uk isn’t set up correctly.

Set up or fix your domain’s PTR record - If you’re the admin for chieftechofficer.co.uk, work with your DNS hosting provider (your domain registrar, Web hosting provider, or ISP) to correctly set up a PTR record for your domain. If you’re using Office 365 to manage your DNS records note that PTR record creation and management isn’t supported in Office 365, so you’ll have to change your DNS management to a DNS host outside Office 365. Refer to this article for more information and instructions: [Change how DNS records are managed with Office 365.]

Unfortunately, Office 365 Support can’t help you fix these kinds of externally reported errors because Office 365 doesn’t support PTR record management.
Original Message Details
Created Date: 13/05/2021 09:12:53


Sender Address: @
Recipient Address: @
Subject: TESTING
Error Details
Reported error: 550 5.7.363 Remote server returned sender verification failed → 550 Verification failed for <@>;No Such User Here;Sender verify failed


DSN generated by: CWLP265MB1970 .GBRP265 .PROD.OUTLOOK .COM
Remote server: ***

This will not be possible on Cloudflares IP addresses.

I suspect that in this situation, the target mail server tried a few different verification mechanisms, and eventually tried to do FCrDNS on your website address. Do you have valid SPF, DKIM and DMARC records for your domain?

The receiving MTA attempted to validate the sender address exists and that failed (nothing related to PTR despite the O365 text). Ensure that the email address being sent from exists in your Exchange org.

And / or the recipient needs to make their MTA suck less:
Office 365 sender verify failed 550 5.7.363 | cPanel Forums

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