Exchange 2016 Activesync Issue

Pabda 21 Reputation points

Installed Exchange 2016 On Premise and removed azure connect. Mail flow works as expected. Mobiles using activesync work if connecting from outside the company. Once staff come in to the office, their phones will not sync within the local LAN with the Exchange Server.

When testing activesync with outlook, only the very first connection pops up with a certificate that is expired. I ran the get-childitem Powershell script on EVERY server. That certificate may very well direct me to the problem, but for the life of me I cannot find it. I know the issuer and expiration date. This falls under the heading of an observation. May not be related.

Error from Outlook when trying to connect within the LAN - cannot connect to the server.

Keep in mind all mailflow works, SSL is good, and activesync works on those same phones if connecting from outside the local LAN.

A strange one, yes. Literally, the same phone that doesn't work, turn off wireless and just use data, and it connects happily.

Suggestions welcomed.

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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Accepted answer
  1. KyleXu-MSFT 26,211 Reputation points


    Based on your description, this phenomenon may be related to the Network in your company:

    When from external of your organization or using mobile data, they mobile device will use the public DNS record to find your Exchange server, so they could to Exchange online.

    When connect to the local LAN, the mobile device cannot find a DNS record which points to your Exchange server.

    So, confirm with your Network team, make sure all DNS records (Such as, You can refer to the DNS records which are configured on public DNS provider) exist for internal devices which connect to the local LAN.

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