On-premise are not receiving email

Occasional Contributor

We are running Hybird environment and since few days on-premise users are not receiving email or would receive late like after hour or so.


I sent one email from office 365 user to on-premise user and run a message trace and found status pending and below error:


Original FQDN and Traget IP is removed from the below error.


Reason: [{LED=451 4.7.0 Temporary server error. Please try again later. PRX5 };{MSG=};{FQDN=abc.ca};{IP=};{LRT=2/29/2020 4:13:41 AM}]. OutboundProxyTargetIP: OutboundProxyTargetHostName: abc.ca


Any suggestions? thank you in advance!

3 Replies
how did you setup your environment, did you setup using HCW ? are there any firewall, are the ports open?

@Adnan Rafique 


Yes we did setup through HCW.


When messages sent it shows pending in message trace and give the below



It would be send if failed then would get a below error: original domain name has been replaced with abc.


Reason: [{LED=554 5.4.14 Hop count exceeded - possible mail loop ATTR34 [QB1CAN01FT015.eop-CAN01.prod.protection.outlook.com]};{MSG=};{FQDN=abc-ca.mail.protection.outlook.com};{IP=};{LRT=2/29/2020 5:16:28 AM}]. OutboundProxyTargetIP: OutboundProxyTargetHostName: abc-ca.mail.protection.outlook.com



In O365 outbound connector i have included on-premise exchange FQDN and our default domain.


Should we removed default domain?




Hello Yousuf khan,
I hope you validated the connector successfully. Just issue might be with Looping the mail from o365 to On-premises. Check with your Default Accepted Domain and keep domain type as Relay. Hope this will solve your problem.