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Exchange 2016 Hybrid - emails sent from Office 365 user not arrivng

fieldj asked
Last Modified: 2018-09-26
Hi all,

I just ran through the Exchange Hybrid configuration wizard yesterday as we want to move some users to Office 365.  

I am currently running through my testing and have found that the user who's mailbox exists in O365 can receive email (both from internal and external email addresses) but they cannot send to either internal or external addresses.

I don't get any non delivery reports or anything like that, the emails just fail to arrive at the recipients mailbox.

I am presuming this is a send connector issue but I am struggling to find the information I need.  Can anyone help point me in the right direction?

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Neha AgarwalSenior Consultant-CG

Please provide the below details:
1.) Trace the mail from O365 portal and check the trace logs and look if you find any information.
2.) Rerun the send connector called “Outbound to Office 365" and validate it and check if it throw any error.
3) Did you create any send connector manually or its the one that created automatically while running the HCW??
4) Did O365 users are able to send mails to O365 users??
5)Did you route outbound mail to external recipients from your Exchange Online organization through your on-premises organization (centralized mail transport), or route it directly to the Internet??
MASEE Solution Guide - Technical Dept Head
Most Valuable Expert 2017

How did you configure your mail flow?
You should see something like this in your Admin center if your Hybrid configuration wizard is ran correctly.
test.pngYou will see and addition Receive connector and Send connector in on premise Exchange server. (sample below).
Receive Connector
test.JPG Send Connector
test.JPGHow did you configure your mail flow?
Please answer this or you let us know how do you want your mail flow.


Yes, I just found those and ran a validation test on the 'Oubound connector'.

I found this was failing.  I am now fairly sure that this is a firewall issue and am awaiting by provider to make some changes.

I will await the results....
Neha AgarwalSenior Consultant-CG

good to hear
MASEE Solution Guide - Technical Dept Head
Most Valuable Expert 2017

Make sure test is succeeded.
Did you see the receive connectors?
If yes. Please run these to avoid issues.
Set-ReceiveConnector "Inbound from Office365" -PermissionGroups AnonymousUsers
Get-ReceiveConnector "Inbound from Office365" | Add-ADPermission -User "NT AUTHORITY\ANONYMOUS LOGON" -ExtendedRights "Ms-Exch-SMTP-Accept-Any-Recipient"

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-->How did you configure your mail flow?
Please answer this
Server engineer
This problem has been solved!
(Unlock this solution with a 7-day Free Trial)
Saif ShaikhServer engineer

This should fix mail flow issue from o365 to onpremise.


Hi all,

I can conform that the firewall was the issue.  
After getting my firewall provider to open port 25 to the IP's listed in the link here:


Everything is now OK.


thanks all

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