Exchange 2010. Additional Mailbox Server

I am currently migrating from exchange server 2010 to 2016. The first step in my migration path is to get all exchange 2010 servers to exchange 2010 sp3 . I have created the exchange server with service pack 3 and I am now migrating users to this new server.

A test user that I have migrated is able to receive mail both internally and externally , send internally but when they send externally they get a mail protection bounce back error from outlook .

Any ideas ?
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Daryl GawnSystem AdministratorCommented:
can you post the bounce back message?
alli87Author Commented:
alli87Author Commented:
the error is posted above
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timgreen7077Exchange EngineerCommented:
That is an O365 rejection, does the user get a bounce back when sending external to anyone other than an O365 user such as gmail, or some other domain. Also does O365 or EOP have any part to play in your external mail routing?
alli87Author Commented:
yes the get bounce backs sending to multiple different domains . There is no link to anything with O365
timgreen7077Exchange EngineerCommented:
is the error the exact same? if so, what are you using for a smart host? are you using EOP?
alli87Author Commented:
the error is always only the first part of the error changes . I just tried a test and a mail went through to a gmail address.
timgreen7077Exchange EngineerCommented:
was the test successful.
alli87Author Commented:
yes it went through to gmail however I tried it with another user and got a bounce back
timgreen7077Exchange EngineerCommented:
what are you using for a smart host for the send connector?
alli87Author Commented:
no smart host just dns
timgreen7077Exchange EngineerCommented:
so to confirm you actually can successfully externally, but not to recipients in o365. is that correct? if you are not sure send test emails to different domains and see if successful.
alli87Author Commented:
can only send externally to gmail . tried O365 and bounce back and tried hotmail and bounce back (hotmail and 365 would be the same platform. Also another domain not on 365 failed
Hani M .S. Al-habshiContributor as IT ExpertCommented:
1-  DNS not resolve some cloud MX records  try to use new send connector
address space  (  * )
route mail through smart host

2-check your ISP if there any  issues ( firewall , delay  )
AmitIT ArchitectCommented:
Error shows your next hop is EOP. Meaning, you need to add this new server to relay message using EOP.

Or you have SPF issue.

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