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Good day!

We have a local installation of Exchange 2019. Services are published through the IIS ARR reverse proxy.

Everything works correctly, including OWA and the Outlook desktop client. But, at some point in time, some clients on mobile devices stop syncing. At the same time testconnectivity.microsoft.com shows that everything is ok.

Manually, this problem is solved if all the user's mobile devices are deleted via the ecp. Then, at the next synchronization, everything starts working as it should.

This affects only a part of the clients, the other part continues to work correctly. Clients with Gmail app on Android and native mailapp on iOS work without any problems.

UPD

Today I received a delivery failure report message with the following text:

We couldn't deliver your message.

Original message details

Created date: 4/21/2023 8:48:02 AM

Sender address: ***

Recipient addresses: ***

Subject: 112

Technical details

MessageDeliveryFailedException: Could not deliver the message [len=70, data=00000000DD3CD10BD698F34E895B24A4A45F42C307008C4F2B6D3011F140B2561F956CC3D7CB00000000010F00008C4F2B6D3011F140B2561F956CC3D7CB0000000098C90000] sent at 4/21/2023 8:48:39 AM.

Failure code: 804f

Is there no information about code 804f

Any suggestions, please?

Alex Whats
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2 Answers2

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The message you got is NDR(non-delivery reports). About the meaning of the error code"804f", you can info this Microsoft Document:enter link description here

Besides ,you issue is similar to the issue on Microsoft Q&A forum:enter link description here. Please check your EAS http proxy log first. Outlook for iOS and Android app uses the Microsoft Native Sync Technology and not the Exchange active sync protocol. Please try to send bypass the ARR proxy and direct to the Exchange server.

falaisi
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  • Thanks for the advice! But the problem suddenly disappeared, while we did not change anything in the server or dns configuration. I hope this does not happen again, but I would like to know the reasons for this behavior. – Alex Whats Apr 24 '23 at 15:59
  • Do you mean the Activesync work fine? There are many factors leading to your problems, it is also may be caused by some chance factors. If the problems do not occur again ,please do not worry ，the previous problem should not appear. – falaisi Apr 25 '23 at 06:50
  • Yes, now all works fine, include mobile, desktop clients and all of this :) Hope the problem doesn't happen again as it's very difficult to debug when some clients are working fine and some are having problems. Good day! – Alex Whats Apr 25 '23 at 07:17
  • Please rest assure that when you met any problem, you can post your issue again. We will still try our best to help you. If there leave any helpful answer to your issue, please mark it as "accepted answer", your kind behavior would help others who also meet the same problem. – falaisi Apr 26 '23 at 07:08
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Did you do absolutely nothing to get this as solved? We do have the exactly same problem, but only when trying to send attachments over 1MB size using mobilephones / active sync. Its kind of strange right now. We installed newest CU for exchange last monday (1week ago) and newest CU for server 2022 last wednesday. Unsure if this occured the problem, as well I cannot find anyone else with this problem, except you :-)

Geh Kah
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