troubleshooting Question

Exchange 2010 to Exchange 2016 on prem migration having major issues

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Matthew CioffiFlag for United States of America asked on
ExchangeWindows 10AzureWindows Server 2016
6 Comments1 Solution70 ViewsLast Modified:
Having major issues with an Exchange 2010 to Exchange 2016 migration.
We installed 2016 on a 2016 server and we are at the point where we are not getting any mail in or out.  Nothing is working at all.  
We have Spamtitan anti spam and our emails are collecting there but nothing is getting into exchange 2010 or 2016.  

I have checked the firewall rules.
I have checked the send connectors and the receive connectors.
I have looked at the virtual directories.
I tried to open everything up by setting the ip ranges in most cases to -

I'm seeing this in the Microsoft Connectivity Analyzer.
Attempting to send a test email message to using MX
       Delivery of the test email message failed.
      Additional Details
The server returned status code 450 - Mailbox unavailable. The server response was: 4.2.0 <>: Recipient address rejected: Greylisted, see
Exception details:
Message: Mailbox unavailable. The server response was: 4.2.0 <>: Recipient address rejected: Greylisted, see
Type: System.Net.Mail.SmtpFailedRecipientException
Stack trace:
at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, Boolean allowUnicode, SmtpFailedRecipientException& exception)
at System.Net.Mail.SmtpClient.Send(MailMessage message)
at Microsoft.Exchange.Tools.ExRca.Tests.SmtpMessageTest.PerformTestReally()
Elapsed Time: 1191 ms.

Anything I try to send from 2016 OWA ends up in the drafts.  I have created a user in the 2016 exchange server new.  that fails as do all older accounts still in 2010.  

Any suggestions?  

Would uninstalling both 2010 and 2016 starting fresh and restoring the old mailboxes from backups be my best bet?  We have like 35 so it is not the worst idea imaginable.  

I have mot yet purchased and installed a commercial cert.  That was next, but might that help?
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