Exchange Active sync Message Size Limit

Hi Readers,

Sharing a small issue that has occurred in our environment as no admin have thought about it previously.

Message size limits that are set for our environment is 25 MB but some of the sales users  Complained that

they are not able to attach document to message that is more then 10 MB in size. We have tested this & found the same thing.

Issue was that in the web.config file (C:\Program Files\Microsoft\Exchange Server\ClientAccess\Sync)

<httpRuntime maxRequestLength=”10240″/> was set to 10 MB.

We have changed it to 25600(25 MB) for resolving the issue.



Sukhija Vikas


11 thoughts on “Exchange Active sync Message Size Limit

  1. Thanks for posting this. Microsoft’s documantation lacks a bit in this case, as they are only refenrencing to the files
    No word of
    There I found the 10MB limit and also increased it. The file was obviously modified by some Update, as it had a timestamp of some day in May 2015.

  2. Hi there,
    Thank for posting!
    I found this.

    3. ActiveSync
    When email is sent using the ActiveSync handheld device the message size is justified with the value located in the file %ExchangeInstallPath%ClientAccess\Sync\web.config

    Default Email message size in Activesync:

    (value in bytes) Approx 9.7 MB
    maxRequestLength=”10240″ (value in kilobytes ) = Approx 10 MB

  3. HI

    we’ve made these modifications to the web.config file and increased the limit to 50MB, however we’re still unable to send emails larger than 20MB from mobile devices (iphone/ipad)
    we have exchange 2010 btw

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