ActiveSync/Cell Phone Email not working after Upgrade

Ford, Edward 6 Reputation points

Hi Guys
We did an Exchange 2013 to Exchange 2019 coexistent upgrade. When I point the DNS to the Exchange 2019 Exchange server cell phone email stops working. If I am on the local network on wireless the phones work no issue. if I am outside the company or only on cellular the email stops working. While on the outside I can delete and re-add my email account to the phone. Computers and laptops work no issue.
what the heck am I missing?
Thank You

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Yuki Sun-MSFT 40,781 Reputation points

    Hi @Ford, Edward

    While on the outside I can delete and re-add my email account to the phone.

    By this, do you mean the email account can be successfully added to the mobile phone but you cannot send or receive messages?
    How about the old messages? Are they synced to the mobile phone?
    Any error messages when this issue occurs?

    Please run the commend below to check the external url for Exchange Active Sync and make sure a valid public DNS record is configured for the host name included in the url:

    Get-ActiveSyncVirtualDirectory | fl externalurl  

    You can also go through the guidance generated by the Exchange Deployment Assistant and check the instructions in the "Configure DNS records" section to see if you have missed anything in your configuration.

    Furthermore, it's suggested to run a Exchange ActiveSync test using the Microsoft Remote Connectivity Analyzer tool and see if we can get any clues for this issue.

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