Your mail server returns this error: 451 4.7.0 Temporary server error. Please try again later. PRX5
Two suggested possible solutions
- ex2013 sometimes encounters problems when you leave the DNS lookups setting in the server properties to "All network adapters", instead you should select a specific NIC or enter the IPs of your DNS servers manually. ECP only configures the transport service, but NOT the the frontend transport service. you can check this with get-transportservice and get-frontendtransportservice and looking at the ExternalDNS and InternalDNS settings. Usually onl theTransport Service would adopt the settings applied to the ECP. Please also configure set-frontendtransportservice with the same DNS settings as the transport service.
- Add the local server's IP to your hosts file: 192.168.1.5 server 192.168.1.5 server.domain.local Restart "Microsoft Frontend Transport" and "Microsoft Exchange Transport" services
( [Online] Microsoft, 2015, Date viewed: 30th August 2015, Ref: https://social.technet.microsoft.com/forums/exchange/en-US/fc26dac5-d4e2-49da-903d-361ea8b85388/451-470-temporary-server-error-please-try-again-later-prx5)