[Migrated from MSDN Exchange Dev]Outlook for iOS and Android Active Sync message size limitations.

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KaelYao-MSFT asked Nov 11, '20 nelsonma-6429 edited Nov 16, '20

[Migrated from MSDN Exchange Dev]Outlook for iOS and Android Active Sync message size limitations.

[Note]
This question was originally asked on the MSDN Exchange Development forum which focuses on development questions on Exchange.
As the former Outlook forums on TechNet have been migrated to Microsoft Q&A forum, we migrated this question manually in order to continue the discussion here.

[MSDN Link]
Outlook for iOS and Android Active Sync message size limitations.

[Original post]
The Outlook for iOS and Android app is not allowing attachments slightly over 10 MB. I believe it may be that if the Outlook for iOS and Android app does not connect directly to our on-premies Exchange servers, instead it seems to connect to a service hosted in Microsoft Cloud. Using the native iOS mail app, it connects directly to our on prem Exchange servers. The native iOS mail app and GMAIL app is able to send emails with attachments over 10 MB.

These were the settings set for our ActiveSync on our on prem Exchange 2016 servers to 35 MB.

 %windir%\system32\inetsrv\appcmd.exe set config "Default Web Site/Microsoft-Server-ActiveSync/" -section:system.webServer/security/requestFiltering /requestLimits.maxAllowedContentLength:36700160
    
 %windir%\system32\inetsrv\appcmd.exe set config "Default Web Site/Microsoft-Server-ActiveSync/" -section:system.web/httpRuntime /maxRequestLength:35000
    
 %windir%\system32\inetsrv\appcmd.exe set config "Exchange Back End/Microsoft-Server-ActiveSync/" -section:system.webServer/security/requestFiltering /requestLimits.maxAllowedContentLength:36700160
    
 %windir%\system32\inetsrv\appcmd.exe set config "Exchange Back End/Microsoft-Server-ActiveSync/" -section:system.web/httpRuntime /maxRequestLength:35000
    
 %windir%\system32\inetsrv\appcmd.exe set config "Exchange Back End/Microsoft-Server-ActiveSync/" -section:appSettings /[key='MaxDocumentDataSize'].value:36700160

Any insight on this?

Thanks!

office-exchange-server-connectivity

· 2

5 |1600 characters needed characters left characters exceeded

Attachments: Up to 10 attachments (including images) can be used with a maximum of 3.0 MiB each and 30.0 MiB total.

KaelYao-MSFT · Nov 11, 2020 at 07:59 AM

Hi,
Since you can use the native iOS mail app and gmail app to send emails with attachments over 10MB, the activesync attachment limit should have been configured correctly.
I notice you mentioned "I believe it may be that if the Outlook for iOS and Android app does not connect directly to our on-premies Exchange servers, instead it seems to connect to a service hosted in Microsoft Cloud",can you confirm it?
And if possible,please also try configuring the affected accounts on a new device and see if the problem persists.

If the response is helpful, please click "Accept Answer" and upvote it.
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nelsonma-6429 KaelYao-MSFT · Nov 13, 2020 at 06:16 PM

Read that the Outlook for iOS and Android app uses the Microsoft Native Sync Technology and not the Exchange active sync protocol. May this be a possibility as to why we are unable send emails over 10 MB via the Outlook for iOS and Android app?

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Answer 1 · 2020-11-13T14:32:22.883Z

nelsonma-6429 answered Nov 13, '20 nelsonma-6429 edited Nov 13, '20

@KaelYao,

We've tried multiple accounts on multiple different devices, all the same result with the Outlook for iOS and Android app. In addition, it would take hours to get a NDR from the Outlook instead of our on premises Exchange servers on the mobile phone, that's why I think the Outlook for iOS and Android App does not connect directly to our on-premises Exchange servers.

Below is the NDR on the mobile device and the message headers of the original email.

Original message details
Created date: 11/8/2020 4:33:14 AM
Sender address: xxxxxxxxxxx
Recipient addresses: xxxxxxxxxxxxx
Subject: 23:32
Technical details
MessageDeliveryFailedException: Could not deliver the message [len=70, data=00000000127228D3C9EAA949BFEC5FEBB957E45A070092857C233CCA064DA4A2473B41CA4EDA00000000010F000092857C233CCA064DA4A2473B41CA4EDA000000004B2F0000] sent at 11/8/2020 4:33:52 AM.
Failure code: f5f0

Message headers:

     From: "xxxxxxxxxxx" <xxxxxxxxxxx>
     To: "xxxxxxxxx" <xxxxxxxxxxx>
     Subject: 23:32
     Thread-Topic: 23:32
     Thread-Index: AQHWtYhFMMfuEa1LLU6K//NKoXp+Xw==
     X-MS-Exchange-MessageSentRepresentingType: 1
     Date: Sun, 8 Nov 2020 04:33:52 +0000
     Message-ID: <SN6PR17MB2640B2A16901656D268E8437F4EB0@SN6PR17MB2640.namprd17.prod.outlook.com>
     Content-Language: en-US
     X-MS-Has-Attach:
     X-MS-Exchange-Organization-SCL: -1
     X-MS-TNEF-Correlator:
     Content-Type: multipart/alternative;
                     boundary="_000_SN6PR17MB2640B2A16901656D268E8437F4EB0SN6PR17MB2640namp_"
     MIME-Version: 1.0

5 |1600 characters needed characters left characters exceeded

Attachments: Up to 10 attachments (including images) can be used with a maximum of 3.0 MiB each and 30.0 MiB total.

Answer 2 · 2020-11-13T17:34:45.33Z

nelsonma-6429 answered Nov 13, '20 nelsonma-6429 edited Nov 16, '20

This is the error from the EAS http proxy log:

 2020-11-13T16:41:29.398Z,67ddb515-32b6-4020-a4ec-0665116b692d,15,1,1979,6,,Eas,xxx-serverxxx,/Microsoft-Server-ActiveSync/default.eas,,Basic,true,******,,Sid~S-1-5-21-3039674024-3586367722-4225467210-4300,Outlook-iOS-Android/1.0,52.96.16.37:49660,********,200,,ClientDisconnect,POST,Proxy,*********,15.01.1979.000,IntraForest,WindowsIdentity,,,,14796248,,,,0,0,,0,,0,,0,0,,0,585,0,479,1,103,,,,,0,1,585,0,,2,,3,585,,?Cmd=SmartForward&User=***%5C***&DeviceId=f6256279b5fc49a39037c025b7f895bc&DeviceType=Outlook,,BeginRequest=2020-11-13T16:41:28.813Z;CorrelationID=<empty>;ProxyState-Run=None;FEAuth=BEVersion-1942063035;RoutingEntry=DatabaseGuid:20053c46-d566-4ce2-b744-b937480194ff%4Server:***********T+1942063035@637408062379136327;BeginGetRequestStream=2020-11-13T16:41:28.815Z;OnRequestStreamReady=2020-11-13T16:41:28.815Z;ProxyState-Complete=ProxyRequestData;SharedCacheGuard=0;EndRequest=2020-11-13T16:41:29.398Z;,StreamProxy=StreamProxy-Request-ExpectReadCallback;HttpException=ClientDisconnect;,,|RoutingDB:20053c46-d566-4ce2-b744-b937480194ff,,,CafeV1

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5 |1600 characters needed characters left characters exceeded

Attachments: Up to 10 attachments (including images) can be used with a maximum of 3.0 MiB each and 30.0 MiB total.

nelsonma-6429 · Nov 13, 2020 at 07:44 PM

Also see a bunch of these 400 errors in our reverse proxy from the ActiveSync command that fail to send/forward emails over 10 MB. It looks like it keeps trying and trying for hours before getting a notification on our mobile device that the message failed to deliver.
We are using IIS ARR reverse proxy.

400 0 64 11916

 2020-11-13 11:43:43 IP ADDRESS POST /Microsoft-Server-ActiveSync Cmd=SmartForward&User=xxxx%5Cxxx&DeviceId=f6256279b5fc49a39037c025b7f895bc&DeviceType=Outlook&X-ARR-CACHE-HIT=0&X-ARR-LOG-ID=8ee2f852-e318-4af3-a57a-313d16a76dee 443 - IP ADDRESS Outlook-iOS-Android/1.0 - **400 0 64 119169**

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KaelYao-MSFT · Nov 16, 2020 at 08:40 AM

Hi,
Thanks for your information and welcome to Microsoft Q&A forum.

Read that the Outlook for iOS and Android app uses the Microsoft Native Sync Technology and not the Exchange active sync protocol.
Within the Microsoft 365- or Office 365-based architecture, Outlook for iOS and Android uses the native Microsoft sync technology as the protocol for data synchronization.
It is a replacement for REST API data sync protocol and doesn't have much to do with this case.

Are there some relevant error events,for example event 1008 in the application log on your Exchange server?

And have you tried sending bypass the ARR proxy and direct to the Exchange server?
Will it also be rejected? If so,will the client receive the NDR mail sooner?

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nelsonma-6429 KaelYao-MSFT · Nov 16, 2020 at 05:10 PM

Hi Kael,

I will try sending the email bypassing the ARR proxy and see if there's a rejection or not.

There are no relevant ActiveSync errors in the application logs on the Exchange Servers. Except for Event 1040:

The average of the most recent heartbeat intervals [205] for request [Ping] used by clients is less than or equal to [540].
Make sure that your firewall configuration is set to work correctly with Exchange ActiveSync and direct push technology. Specifically, make sure that your firewall is configured so that requests to Exchange ActiveSync do not expire before they have the opportunity to be processed.

For more information about how to configure firewall settings when using Exchange ActiveSync, see Microsoft Knowledge Base article 905013, "Enterprise Firewall Configuration for Exchange ActiveSync Direct Push Technology"

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