Exchange 2016 + Outlook on iOS and Android: Message size limits and their configuration

Users with the official Microsoft Outlook client on Android or iOS kept running into ~36MB size limits when attempting to send attachments (given the megapixel sizes of most cell phone photos, this can amount to 3 to 4 pictures attached and the whole message is rejected), and none of the conventional transport/mailbox maximum size settings were the cause. I’m hoping the changes in the following articles are the fix:

The settings I specifically believe are responsible are:

  • maxAllowedContentLength in %ExchangeInstallPath%FrontEnd\HttpProxy\ews\web.config
  • maxAllowedContentLength and maxReceivedMessageSize in %ExchangeInstallPath%ClientAccess\exchweb\ews\web.config
  • maxAllowedContentLength and maxRequestLength in %ExchangeInstallPath%FrontEnd\HttpProxy\owa\web.config
  • maxAllowedContentLength, maxRequestLength and maxReceivedMessageSize in %ExchangeInstallPath%ClientAccess\Owa\web.config

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