Exchange 2016 - Not Sending or Receiving any Internal or External email

[AIT]

Hi All,

 

Firstly we have seen this issue in the past but this one is currently defeating us. were 24hours in looking at this and nothing seems to get it to work. (not even for a short period of time)

Local school has a single Exchange 2016 server. was on Update 8 and we have updated to 13 and now 14. Makes no difference.

 

I'm aware a lot of these issues are caused by DNS being incorrect or set with multiple or external. We have ensured that its set to a local AD server and this server can resolve any MX record and added its name and FQN to the hosts file record.

 

Error received:

External servers are reporting the exchange server is issuing: Deferred: 451 4.7.0 Temporary server error. Please try again later. PRX4

Internal Email gets a similar log in transport logs: SmtpResponse:451 4.4.395 Target host responded with error. -> 235

 

Our Diagnostic:

Transport services are all started and Active on exchange / certificates are valid

Google reports this could be a DNS issue, and we have done every check. DNS is functioning properly and tried to put the local entry within the hosts file.

 

Id be massively grateful if anyone has any ideas.

[forkies]

Nobody has been messing around with the send/receive connectors have they?

[AIT]

Just to throw a little bit more out there. I have restored Exchange from 4 days before (when it was functioning properly) however powering this up has exactly the same fault. So does anyone know of anything else that can effect exchange in this manor?

 

And I think the above answers the send receive connector question. I have re done all send receive connectors. So no, i dont think its even exchange now.

Edited October 17, 2019 by AIT

[kjadams]

Our Exchange 2010 stops sending and receiving when space on the C:\ is less than about 5GB. Logs and data stores are on separate drives.

[AIT]

C has 50GB Free

Datastore drives (3 datastores on 3 drives) equally have plenty of space, one of our first test was to add around 20GB per drive.

 

As above really. Must be something outside of the exchange box, to have a working exchange restored and not work.

[HPlum78]

https://docs.microsoft.com/en-us/exchange/troubleshoot/mailbox-configuration/dns-query-failed

Is the MS take on this....

[AIT]

Hi All,

 

Ok so we have resolved it. IT was GPO. We have dropped exchange into its own GPO and blocked inheritance. (so no policies apply) - GP Update and within 3 mins emails start flowing again.

 

We don;t hold complete management of the site so have asked the local IT Team to let us know what they were playing with so we can highlight the specific GPO that caused it to stop.

 

Very interesting error and never heard of GPO stopping email!!