setup/migration issue with Exchange 2016

Hi Guys,

I'm having an issue migrating exchange 2010 to 2016.

I'm on the phase that had exchange 2016 setup and coexists with 2010, but when I try to send emails from a new mailbox in OWA, it failed both internally and externally. the emails will just sit in draft. the new mailbox does receive emails either.

so far I only created an internal relay connector and everything else is default.

im stuck here, any suggestions?
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Jose Gabriel Ortega CastroCEOCommented:
In the coexistence phase you need to change all (mx, records and virtual folders to the newest server, this case 2016). and you need to create a send conector to internet so the emails can go out and in, over the new server, also the new server will manage the mailflow into the legacy server (2010).

Try creating the send connector, if you already did that changes:
SysToolsData Expert - Recovery,Backup,MigrationCommented:
Cause: If Email items will remain in the Drafts folder and not stored and passed the transport system, means the transport service is not running on available server properly.

If Mailbox Transport Service is not running on the mailbox server that hosts the active database for the user’s mailbox and email items remain inDrafts folder until the services come Online and Exchange is able to process outbound items.

Note: If Send and Connector and Receive Connector details are correct then it can be Incorrect DNS binding to server NICs is one of the problem.

To know more:
manav08Author Commented:
the Hub transport connector you can see in the first screenshot is from the exchange 2010, it just showed up when i finished installing exchange2016, in this send connector, under Scoping->Source server, there were only the 2010 server there, i then added in 2016, after that, all the emails from 2016mailbox were stuck in Draft,  i just deleted 2016 from source server, then all the emails moved to sent, but those emails are actually stuck in email queue now, showing error 451 4.4.397 as in the attachment.
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Valentina PerezExchange ServersCommented:
Hi Manav,

It seems that Excahnge 2016 is not able to send email. Please check that the port 25 is open in the Exchange 2016. Check that all the services are running in both exchange.

Check with the following command: Test-ServiecHealth

Vidit BhardwajAdminCommented:
If the mailbox is on 2016 make sure msexchange transport delivery and submission service is running.
manav08Author Commented:
Hi Vidit Bhardwaj,

both services are running. Test-ServiceHealth returned all "True".
so i have made following fixed so far,
deleted Exchange 2016 server Secondary DNS, this seemed fixed stuck in draft issue.
re-added exchange2016 to send connector.

now send/receiving both working fine on 2010 server, but 2016 won't send to/receive from 2010 server, neither to the internet, only two 2016 mailbox can talk to each other.
manav08Author Commented:
Hi Valentina,

port 25 is listening, telnet worked on that port, and Test-ServiecHealth returned "true" on both servers.

I have faced this issue previously with one of my client

Check dns setting on your exchange server under network card properties
U must have pointed exchange to public DNS sever such as google dns or even loop back (
Just remove that entry and ensure that exchange is pointing to DC only under preferred and secondary dns
Now reboot exchange server and you should go through
Same time ensure that domain controllers also do not point to public dns servers under network properties, if do, remove those entries and restart netlogon and dns server service on domain controllers

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manav08Author Commented:
yep, the NIC's secondary DNS was pointing to, all good after deleted it.
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