Email flow issue between On premises to Exchange Online users. RRS feed

  • Question

  • Hi Folks,

    A customer is currently running on-premises Exchange 2010 and 2013 with Exchange Online Protection (EOP). All Emails flow through EOP to on-premises Edge Transport 2013 Servers.

    Customer wants to evaluate Exchange online so we have set it up by running Hybrid Configuration Wizard (HCW) through Exchange 2013 and we have migrated couple of test users.

    what we did we disabled two connectors in office 365 portal created by HCW and we left the on premises send connector created on On Premises Exchange by HCW as per our logic there should not be any issue since EOP and connectors are already in place.

    Now, what is happening - On premises users can not send email to Exchange online user although Exchange online user can send email to On Premises user as well as to hotmail/ external users without any issues.

    We have monitored queues on On Premises infrastructure and we are getting following message on message Queue.

    “451 4.4.0 Primary target IP address responded with: “451 5.7.3 Cannot achieve “Exchange Server authentication”.” Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts”

    and we also got NDR with following message:

    "Remote Server returned '554 5.4.6 Hop count exceeded - possible mail loop'"

    Please assist since Office 365 support folks could not resolve this issue.

    Thanks, Sheeraz

    Sunday, August 21, 2016 11:23 AM

All replies

  • First check the receive connector configuration on the Exchange server. The default connector is usually used and you need to ensure that Exchange server is enabled as an authentication type. To get in detailed:

    However, you may also get help from below informative resources might helps you to resolve this issue and lets you to get this job done:

    Office 365 mail flow troubleshooting index 

    Office 365 – Common Exchange Online Hybrid Mail Flow Issues

    Hope this helps!

    Cloud migration can be a tedious task without the right solution. Lepide Meteor suite has all you need to analyze/upgrade/migrate your current Exchange environment to Office 365 and also helps you to easily Import/Export & convert EDB, PST and OST into new or existing PST files.

    Monday, August 22, 2016 6:52 AM
  • Hi,

    According to your description, I know that On-premise user cannot send message to Exchange Online user after disable two connectors in Office 365, however it works from Exchange Online to On-premise.

    If we deploy Hybrid environment, we need connector for mail flow between On-premise and Exchange Online. Please enable those connectors in Exchange Online: Sender connector(used to send message to On-premise user) , Receive Connector(used to receive message from On-premise user).

    More details about it, for your reference:

    Please remember to mark the replies as answers if they help, and unmark the answers if they provide no help. If you have feedback for TechNet Support, contact

    Allen Wang
    TechNet Community Support

    Monday, August 22, 2016 8:02 AM
  • We have enabled two connectors those we disabled in Office 365 - Exchange Online Connectors but it email flow is still not working between On Premises to Exchange Online users.

    After going through many available resource on TechNet we identify that Exchange 2013 cannot submit message queue to 2013 Edge Transport Servers.

    Can anyone let us know what would be correct Receive Connector setting on 2013 Edge Transport Servers with Authentication etc?

    Thanks, Sheeraz

    Wednesday, August 24, 2016 9:17 AM