I have a customer on Office 365. When they send an email to a particular recipient, they get an error:
A security check at "recipientdomain.com" failed due to misconfigured settings at "sendersdomain.com."
Status code: 550 5.7.363
It appears that the recipient's email server at recipientdomain.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 sendersdomain.com isn't set up correctly.
I know that if the sending email server is in-house, I would contact the ISP and have them create an rDNS entry but how do we fix this if the sending server is Office 365?