Thursday, August 27, 2015

Setting properties via EWS on a Draft message in a Compose Mail App

With the latest updates that have been released recently for Compose apps that are now available in OWA in Office365 and the Office/Exchange 16 preview the ability to extend what your compose apps can do has been greatly enhanced. With version 1.3 of the API you can now save an Item via the saveAsync method .

Why this small change is important from an extensibility point of view is that when you save an Item this way, it creates a draft in the Mailbox you activated the compose app from which you can then modify anyway you like using the EWS updateItem operation. (normally you would be restricted in a compose app to just using the subset of properties and methods provided for in the Office.js).

One trick however is the ItemId which you need to make an UpdateItem EWS Request to update the Draft Item is still only available in Read Mode. So to get around this I've come up with the following workaround

  1. Set a custom property on the draft Item using the Mail App Custom properties method using something like . With my Mail Apps I generate a new GUID for the app session that I use as the value.
  2. Save the Item your composing as a Draft using saveAync
  3. Now you can use makeEwsRequestAsync to do a findItems on the drafts folder of the Mailbox with a restriction so it only finds the Item with the Custom property you have set. The Custom properties you can set in the Mail App API are documented in . But basically what you have is they are a named property within the PS_PUBLIC_STRING propset of type String. The property name of the property is prefixed with cecp- and rest of the property name is the GUID of your Mail Apps as defined in the application's manifest Id .
  4. Once you have the ItemId and Change key you can then use UpdateItem in EWS to update any of the extended or strongly type properties on the draft Message.
One thing to note to use this workaround your Mail App needs the ReadWriteMailbox privilege to allow the use of the EWS Operations. I've put together a sample of using this workaround in my OWA Voting button app.

Also because this is using version 1.3 of the Mail App Api you should set the requirements in the Manifest file of your application eg

    <Sets DefaultMinVersion="1.3">
      <Set MinVersion="1.3" Name="Mailbox"></Set>

This will mean your Mail App will only activate in clients that support version 1.3 which means at the moment it won't activate in Outlook 2013.


Guillaume BRAUX said...

Hello Glen,

I have followed your exact and clear workaround to be able to add an extended property through EWS during the message compose.
My EWS request is successfull, but my property does not appear in the sent message. It is like if the local message in the compose windows takes precedence over any server-side that may have happened before send (and that are then discarded).

FYI, if I try to add the property through EWS after message is sent, it works.

Or is there any kind of resync that should be done before message is sent so it keeps ews defined properties ?

Thanks for your feedback !

Guillaume BRAUX said...

(notice that I am composing an appointment, not an email ... But is should be the same, right ? ;()

Guillaume BRAUX said...

And also, after adding the custom property through EWS, if I close the current compose windows, and re-open the item by selecting the draft calendar item ... I now got the custom property !

So it looks like the local email overrides any changes chat could have appened on the sever-side in the meantime ...

Any idea of a workaround of the workaround ? ;-)

Glen Scales said...

Appointments are different from Email, I would say you would need to save the appointment with the custom property with no attendees then add the attendees back and update. It may require multiple operations

Anonymous said...

Hi, When i create an email message through Graph API, It has been created as a DRAFT, Not as an actual Email, Eventhough in EWS API, They are saying, It has been Created as a DRAFT. Is there any way in API to create it as an Actual email. The above solution you say it in a blog is related to that? Please assist me