Hi Everyone,
Customers email the ITHelpdesk distribution group from outside of my organisation. My team and an external contact are in this DG.
The external contact is a monitored by our cloud based service desk application and logs all emails sent to it automatically into our online service desk.
All the staff in the DG get the clients emails internally just fine however the clients get an NDR telling them the message sent to the external service desk contact failed and calls are thus not getting automatically logged in the service desk.
The NDR says...Remote Server Returned '550 Administrative Prohibition'
DG setting already has Authentication disabled (RequireSenderAuthenticationEnabled : False) and this system has worked for as long as I can remember but is now not and giving this error. No changes my side.
P.S. I push out all of our mail via a 'smarthost' configured send connector with username and password managed by the 'smarthost' company.
I'm arguing with them this is an error on their side and they are arguing that this an error on my internal exchange?
Any ideas where this is being blocked and how I can resolve this?
Thanks in advance,
durrie.