How to test mail flow in Exchange 2019 in an existing Exchange 2013 environment.

Copper Contributor

Hi experts,

I'm trying to complete the upgrade process from Exchange 2013(on-premise) to Exchange 2019(on-premise).


I did all the steps that are explained in Best Practice for Upgrade and the Upgrade Assistant from Microsoft experts. Also, I'd like to thank you for them.


But what is my question?

There are 2 Exchange 2013 servers in my domain with more than 2000 users. I installed new Exchange servers and all work fine in the organization.

Regarding our business, I can not take a risk and start mailbox migration directly and would like to test all things in the new environment first, like OWA, Outlook, and all related things to the new environment. I created some databases on the new servers and some users on them to test mail flow on these servers.

The problem that I have is, that I can connect directly to new servers in OWA to and work with test users, and mail flow there works fine. But when I try to use Outlook to test, it can not find new servers. 

I think my issue is autodiscover record in DNS but I can not change it at the moment, because the old environment is working. When I change this record on the new servers to itself( and try to configure a profile on Outlook manually and set the mail servers on the new server directly, Outlook still can not find the servers.


What is your suggestion to have a test way in my case? I searched so many articles to find a way but it seems in this way, there is no solution. I don't want to create a new zone for the test, because in the External mail flow test, I will need an SSL certificate.


I appreciate any help or ideas that you can provide.


Kind Regards,


7 Replies

Hi @hassanshakeri,

regarding your question, you can use the Test-Mailflow Powershell cmdlet to diagnose whether mail can be successfully sent from and delivered to the system mailbox on a Mailbox server.

You can also use this cmdlet to verify that email is sent between Mailbox servers within a defined latency threshold.

Here are the steps to test mail flow in Exchange 2019 in an existing Exchange 2013 environment:

Open the Exchange Management Shell on the Exchange 2019 server.
Run the following command:

Test-Mailflow -TargetEmailAddress <email_address>

Replace <email_address> with the email address of the recipient mailbox.
Verify that the test message was delivered to the recipient mailbox.

You can also use the Test-OutlookConnectivity cmdlet to test Outlook connectivity. Here are the steps to test Outlook connectivity:

Open the Exchange Management Shell on the Exchange 2019 server.
Run the following command:

Test-OutlookConnectivity -ProbeIdentity OutlookSelfTestProbe

Verify that the test was successful.

Test-Mailflow (ExchangePowerShell) | Microsoft Learn
Best Practices for Migrating from Exchange Server 2013 to Exchange Server 2019 - Microsoft Community...
Mail Flow issues after mailbox migration Exchange 2013 to 2019 (

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Kindest regards,

Leon Pavesic

Hi @LeonPavesic 

thanks a lot for your answer. But it seems my question was not clear.
The mail flow is working fine and all emails are sending and receiving between mailboxes in both server environments. I can test and check them in OWA.
The problem is, when I create a profile for Outlook in the Mail option in the control panel, and then I Open the Outlook app, it can not find the new servers to connect. It stays there for a long and at the end tells me in an error, that I can not find the proxy server security.



Outlookselftest from the new servers has successful results. :face_with_rolling_eyes:

This is my main issue and I can not find the reason why Outlook can not find the servers. Is there something wrong with the configurations? I have no more idea.

I compared all settings between old and new servers and all seem right.




When I need to perform functional testing like this I do it from a workstation that has a hosts file that points the DNS names used for mail to the new servers. Make sue you capture all the DNS names used to connect to Exchange in the hosts file

@Dan Snape 

Thanks for your reply. I edited the host file to address Outlook to the new servers before. But it still can not find the servers. I pointed the mx and autodiscover record to the new servers. If there is any other DNS that should be pointed to the new environment?


Kind Regard,


Try and do a test using the Outlook Test email auto configuration utility. That will give you some ideas of what might be going wrong. If you've got the host file pointing all DNS names required to the new servers (I'm not able tell you what DNS names you're Exchange environment is using), then I'd say you've got something blocking network connections to the new Exchange servers.

Hi @Dan Snape and thanks a lot for the time to answer me.

What I don't understand is, if my way is the right way. 

short explanation again:

There are 2 servers in a domain configured on an LB. ex1 and ex2 in production. So we have an MX record for this area.

servers : &

mx record:



Now, I installed 2 new servers as Exchange 2019. What do I want to test? I created some mailboxes on the new servers' databases and I want to test mail flow just on these two servers.

I have a test laptop and I edited the host file to:




new server IP

new server IP

In this way, my goal is that the test laptop will just connect to the new server.


As I on top mentioned, I can connect directly to the servers per browser with 443. But when I run Outlook, I get those errors. This I can not understand.


I'm sorry to bother you with the long post but I appreciate it if you have any ideas here.


Kind regards, :)


Sounds right, but I'm not sure why you are getting the errors. It could be a bunch of misconfiguration, but to me it sounds like your network (ie firewalls, LBs, network devices, proxy) is blocking client traffic in some way. as I said, the Outlook Test email auto configuration utility will give some details of why Outlook is failing.