1 MB response size limit with outlook web add-ins

Question

I'm using makeEwsRequestAsync to get the full MIME content of the email. But it looks like response size is capped at 1 MB, per the error message in the response:
"ErrorMessage":"Response exceeds 1 MB size limit. Please modify your EWS request.”

<GetItem xmlns="http://schemas.microsoft.com/exchange/services/2006/messages">
  <ItemShape>
    <t:BaseShape>IdOnly</t:BaseShape>
    <t:AdditionalProperties>
        <t:FieldURI FieldURI="item:MimeContent"/>
    </t:AdditionalProperties>
  </ItemShape>
  <ItemIds><t:ItemId Id="' + itemId + '"/></ItemIds>
</GetItem>

I need to get MIME content of messages which may exceed 1 MB, and also POST such content to our server. Is there any way to increase this limit in the request, or configure this on the Exchange side?

Answer 1

It is not possible to make EWS requests to the client side that exceed 1 MB, however you can give your server the information that it needs to make the request itself.

You first need to call Office.context.mailbox.getCallbackTokenAsync which will give you a token you can use to make EWS requests from your server.

Then you will need to get the item ID which is available through Office.context.mailbox.item.itemId.

Finally, you need the url to make the request to, which is Office.context.mailbox.ewsUrl

With these 3 pieces of information, your server can make the SOAP call to EWS from your backend, and bypass the 1 MB limit imposed on the client. At this point, you can pass whatever information needed back to your client.