OWA or Outlook on the Web have never quite had the feature parity with the desktop version of Outlook which can be a point of frustration for those primarily using it. Although interesting in Office365 new features like clutter, sweep etc are now lighting up in the OWA first before they make their way into new desktop releases. One of the things you haven't been able to do previously with OWA is create an Email with voting buttons. With compose apps and some of the recent changes in version 1.3 of the API which I posted about here, you now have the ability to add some of this functionality back in. Actually with a little imagination you also have the ability to actually build something a lot better then the voting buttons feature which have been around in Exchange for some time. But in this post I want to show how you can create a Compose Mail App that uses EWS to make changes to the draft message to enable the feature.
One thing also to note is that creating an Email with Voting buttons isn't supported also in EWS so I'm using a workaround of generating the PidLidVerbStream property value using the documentation from https://msdn.microsoft.com/en-us/library/ee218541(v=exchg.80).aspx . The one issue you can have is if you don't get the value of this property correct this can cause Outlook to crash (which means you then need to delete the offending item with mfcMapi). So this Mail App would be unsupported, experimental and largely untested.
Here's a screenshot of what the Apps looks like in Action
After you select the Voting option you want you need to hit the Save button which will invoke the actions to modify the draft message.
I've put the code for this MailApp up on my GitHub repo https://github.com/gscales/MailApps/tree/master/OWAVoting if you decide to test it and find any bugs please submit them back. As I mentioned before you should consider this experimental only. All the code is included in the script.js file and uses the workaround I described here as this was only a test app I haven't put any error processing in the Aysnc callbacks.