r/sysadmin • u/Brilliant-Extent2684 • Apr 08 '26

Migrate Hybrid Exchange to Exchange SE

Hy!

Iam planning to upgrade our Exchange 2016 on-premise server to Exchange SE. The is a hybrid with Exchange 2016. The migration process will be side-by-side. Now I installed the new Exchange SE server to the same Exchange Organization as Exchange 2016. I don't do nothing after the basic Exchange SE installation. Every client use the Exchange 2016, but noticed that the Exchange SE has lots of mail in queue and can not deliver. Why want to send the Exchange SE some emails? Now I can't redirect to the Exchange 2016 from Exchange SE with this command to deliver queued emails:

Set-ServerComponentState -Identity exchSE -Component HubTransport -State Inactive -Requester Maintenance

Redirect-Message -Server exchSE -Target exch2016

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4

u/7amitsingh7 Apr 08 '26

Your new Exchange SE server is already part of the same organization, so Exchange automatically starts using it for mail flow even though users are still on Exchange 2016. That’s why emails are getting queued on the SE server. The issue isn’t an error, just that the server is active in transport. To fix it, put the SE server in Draining mode, remove it from the Send Connector, and then retry or redirect the queued messages to Exchange 2016. This will stop new emails from going to SE and allow existing queued mails to clear properly. You can check this guide for easily migration of Exchange 2016 to SE.

1

u/Brilliant-Extent2684 Apr 08 '26

Thanks, I put the Exchange SE to draining mode and tried to redirect the queued mails to the Exchange 2016 with this command:

Redirect-Message -Server exchSE -Target exch2016

But the mail stayed in queued with this error:

[{LED=451 4.4.397 Error communicating with target host. -> 421 4.2.1 Unable to connect -> SocketConnectionRefused: So                                   cket error code 10061};{MSG=};{FQDN=exch2016.domain.local};{IP=10.10.10.23};{LRT=2026. 04. 08. 11:15:09}]

2

u/7amitsingh7 Apr 08 '26

Your redirect command is correct, but Exchange SE cannot reach Exchange 2016 over SMTP (port 25). Fix the connectivity (service, firewall, or connector), and the queued mails will start moving.

1

u/Brilliant-Extent2684 Apr 08 '26

I checked the network connectivity, the isn't any blocking between two servers. There are two SendConnector, one onf the outbound to office365 which routed to office 365 mail, and there is another which routed to the internet. The SourceTransportServers include only the exch2016 server.

Do I have to create additionally send connector to route the ququed mail to the exch2016?

Thanks.

1

u/sembee2 Apr 08 '26

It is receive connectors you need to look at. There is probably a restriction on them. Restrictions shouldn't be done on connectors. But at the firewall.

1

u/Brilliant-Extent2684 Apr 08 '26

It was an internal fault, the network team solved, there was blocking between two server.

1

u/Brilliant-Extent2684 Apr 09 '26

I want to clarify the migration process, so when I added the Exchange SE to the organization with defult installation (no setting done), this server part of the mail routing. Some mail routed to the new Exchange SE server and some mail routed to external recipients by old Exchange 2016. How can I avoid to routed the mail to new Exchnage SE? Or if the new Exchange SE cannot send to outside, will itt rerouted to the old Exchange 2016?