Office.js: MakeEWSRequestAsync throws “The request exceeds the 1 MB size limit. Please modify your EWS request”

One of my customer created Outlook Web add-in (Office.js) and when he calls mailbox.makeEwsRequestAsync method. But they got the following error “The request exceeds the 1 MB size limit. Please modify your EWS request”.

At the app level, the developer is making the call from web add-in to create a mail item in drafts folder via EWS request. So I took a step back, looked at the method – it makes an asynchronous request to an Exchange Web Services (EWS) service on the Exchange server that hosts the user’s mailbox.  So this method sends an EWS request on behalf of the add-in to Exchange. Your add-in must have the ReadWriteMailbox permission to use the makeEwsRequestAsync method.

When we debugged further we noticed once they cross more than 1 MB number of characters they see this error. This is by design and documented this limit here. So please aware about this limit (1 MB number of characters) for a request or response to a Mailbox.makeEwsRequestAsync call.