I have exhausted efforts on a report from users that get mail to a accepted domain setup that a coupld of senders are getting NDR.
Generating server: server-4.bemta-7.messagelabs.com
acceptedomain.com #<acceptedomain.com #5.0.0 smtp; 550-Please turn on SMTP Authentication in your mail client. > #SMTP#
I checked the senders(two unrelated ones) and their mxrecords show messagelabs.com
I have used mxtoolbox and other tools to send smtp mail to our accepteddomian.com and see it in our mxlogic filter audit trail but never mail come from the two sender domains.
Request for them to provide confirmation they are trying to send to our correct servers fia smtp log snippet are denied and said not to be their issue and handled by their corporate and mail was working before the 29th.
I have confirmed all things propogated correctly foru our servers and mail to our primary domain for our org gets through no issues.
Any suggestion on what other routes I can investigate.