Forum Discussion
Hybrid Exchange change of SMTP relay connector
Hi All
So we have Hybrid Exchange environment, with few 2010 Exchange boxes on-prem, 1x Exchange 2016 on-prem (as the hybrid) and O365 tenant.
Until now we were using one of the EX2010 boxes as main smtp relay and it`s working great. Now we want to switch that role and move it to the hybrid 2016 Exchange. To beused by the internal scan2email, apps, etc for sending anonym.
All FW rules are configured correctly.
The ext IP address of the 2016 box is added as trusted connector in EXO
I have send/recieve connectors configured on the 2016 box
The problem:
If I go and test telnet (EXO ext IP) 25 - from within the EX2010 box, I got connection and response and all is nice and shiny
If I try to do the same from the hybrid 2016 box - got connection open and blank screen. Stays for about 60 seconds and then Connection closed. No need to say that it is not forwarding anything if I try lets sat scan2email from one of the printers.
I found in the logs some errors saying socket error - but it doesnt make sense because the fw shows all connections as allowed and as I said the fw rules are the same for EX2010 and EX2016 boxes, the difference is that they are presented with different ext IPs, but both of them added as trusted in EXO Admin
Any ideas? I cant find any other reason why it would not establish smtp connection to the EXO ?
Whenever I setup a connector for this purpose on an Exchange 2016 Server, I always set the security tab options as follows;
I would definitely double and triple check your firewall rules too. Do you definitely have the Exchange Online IP's all allowed for the Exchange 2016 server?
8 Replies
It sounds like there might be a configuration issue with the SMTP relay connector on your hybrid Exchange 2016 server. Double-check the connector settings to ensure they match those of the Exchange 2010 server. Also, verify that the firewall rules are correctly configured to allow traffic from the hybrid server to Exchange Online. If the issue persists, consider reaching out to your IT support or consulting with a Voice SMS Service Provider for assistance.
Check the Exchange 2016 box for any particular settings or limitations that may be causing the connection issue, such as IP restrictions or authentication settings.
In addition, confirm that DNS resolution and network connection from the Exchange 2016 machine to Office 365 are working properly.
Finally, check any recent modifications or additions to the Exchange 2016 setup that may affect SMTP relay services operation.
If the problem persists, it may be helpful to engage with Exchange professionals or Microsoft support for more troubleshooting and solutions.
The issue could be related to the hybrid Exchange 2016 box. The EX2010 box connects properly, however the Exchange 2016 box fails to connect despite having the correct firewall rules. Check the Exchange 2016 box's SMTP relay and connector configurations. Check the IP trust settings in Exchange Online Admin. Investigate any socket failures in the logs. If problems persist, consider contacting Exchange support or checking network parameters for differences. Additionally, confirm compatibility with the SMTP relay service provider, as this may impact connectivity.
Hmm, that's interesting. Are you able to share a screenshot of the receive connector you have created on your Exchange 2016 server please?
Also, could you share the socket error you are seeing too?
PeterRisingthanks for the reply
this is the receive connector (screenshot) and under security we have marked ONLY - Anonymous
Scoping is the internal printer network
Looks like the receive connector on the Exchange 2016 is ok, but then if try to open SMTP 25 to Outlook.office.com from the Exchange 2016 all I am getting is blank screen and nothing else. When I try to do the same from the old 2010 Exchange box it all works perfectly. As I said on the FW both boxes have identical rules. Not sure why EXCH2016 -> Outlook.office.com:25 not working
Whenever I setup a connector for this purpose on an Exchange 2016 Server, I always set the security tab options as follows;
I would definitely double and triple check your firewall rules too. Do you definitely have the Exchange Online IP's all allowed for the Exchange 2016 server?
