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Outlook for IOS and Exchange 2016 - Attachment size limit issues

PALERMO Dario 1 Reputation point
2020-08-18T22:33:20.107+00:00

When trying to send email from Outlook for IOS, when the attachment are above 35 MB we get the attached error (it's in italian but it means that the draft size must be under 35MB.

All connectors have 50MB limit, in the web.config files I've got well above 35MB (the standard EWS settings is 67108864).

I started following this article:

https://learn.microsoft.com/en-us/Exchange/architecture/client-access/client-message-size-limits?redirectedfrom=MSDN&view=exchserver-2019

and then I changed the limits for both OWA and Activesync to 67 MB.

Also, the same email can be sent from IOS Mail App (it uses ActiveSync I think).

Any suggestion?

Thanks bye, Dario

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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. Andy David - MVP 142.8K Reputation points MVP
    2020-08-18T22:55:20.513+00:00

    The limit for the Outlook app is 33MB.
    https://learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits#message-limits-1

    I know what you are thinking, "what does this have to do with me?"

    Well, the architecture of the Outlook app is one where the data is actually synchronized and dependent on Office 365, so their limit is yours: 33MB for the Outlook Mobile App.

    https://learn.microsoft.com/en-us/exchange/clients/outlook-for-ios-and-android/use-basic-auth?view=exchserver-2019

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  2. Lydia Zhou - MSFT 2,371 Reputation points Microsoft Employee
    2020-08-19T07:27:07.467+00:00

    Since Microsoft Q&A forum is a public platform, we helped cover the domain name in your image, please pay attention to your personal information next time.

    Except EWS limits, did you also check the ActiveSync limits in web.config file? Are they default settings? Please don't forget to check settings both for frontend and backend, and pay attention to the unit these values use.

    Do you deploy any proxy server in your organization?
    You can check if there are any limits or configuration on the proxy server side which can contribute to this issue as well.

    In general, the file attachment size limit for Outlook for iOS and Android is 25 MB for Exchange server users. For your reference: Message limits across standalone options.