Why doesn't using EAS to sync Drafts from server to client work anymore?

Question

Hi All,
I understand that uploading an email into a Drafts folder is not possible and has never been possible using Exchange ActiveSync.
It has always been possible, however, to download emails from the Drafts folder and to sync the Drafts folder like any other folder. Recently, however, I have been having problems performing this sync. These problems are occuring on Office-365. Other users
are also experiencing the issue. There is a thread discussing this issue  on that site at: http://community.office365.com/en-us/forums/158/p/176113/525322.aspx#525322 
Unfortunately, there is still no resolution forthcoming from the Office-365 support team, so I thought it might help to cross-post the problem here.
In short, the problem that I am seeing is that the GetItemEstimate command receives a Status of 4 indicating an invalid sync key. This is even though the Sync Key is known the be valid. If that issue is ignored, and a Sync command is sent, then there is no
error, but the incorrect information is returned. The information that should be returned is the 'Adds' for the folder. Instead, an empty reply is received, indicating that there is nothing to sync.
Here are the details from the interaction:
=================
 [EAS] Client Sends: 
================
<Sync xmlns="AirSync:">
    <Collections>
        <Collection>
            <SyncKey>0</SyncKey>
            <CollectionId>4</CollectionId>
        </Collection>
    </Collections>
</Sync>
======================
[EAS] Received from Server
======================
<Sync>
    <Collections>
        <Collection>
            <SyncKey>1335200247</SyncKey>
            <CollectionId>4</CollectionId>
            <Status>1</Status>
        </Collection>
    </Collections>
</Sync>
=================
 [EAS] Client Sends:
=================
<GetItemEstimate xmlns="GetItemEstimate:">
    <Collections>
        <Collection>
            <airsync:SyncKey>1335200247</airsync:SyncKey>
            <CollectionId>4</CollectionId>
        </Collection>
    </Collections>
</GetItemEstimate>
======================
 [EAS] Received from Server
======================
<GetItemEstimate>
    <Response>
        <Status>4</Status>        
        <Collection>
            <CollectionId>4</CollectionId>
        </Collection>
    </Response>
</GetItemEstimate>
================
[EAS] Client Sends
================
<Sync xmlns="AirSync:">
    <Collections>
        <Collection>
            <SyncKey>1335200247</SyncKey>
            <CollectionId>4</CollectionId>
            <DeletesAsMoves/>
            <GetChanges/>
            <WindowSize>64</WindowSize>
            <Options>
                <airsync:MIMESupport>2</airsync:MIMESupport>
            </Options>
        </Collection>
    </Collections>
</Sync>
=====================================
This receives an empty reply indicating no changes
Here are the HTTP Headers:
=====================================
Headers: {
    "Cache-Control" = private;
    "Content-Encoding" = gzip;
    "Content-Length" = 119;
    "Content-Type" = "application/vnd.ms-sync.wbxml";
    Date = "Fri, 19 Jul 2013 22:31:47 GMT";
    "MS-Server-ActiveSync" = "15.0";
    Server = "Microsoft-IIS/7.5";
    "Set-Cookie" = "X-BackEndCookie=S-1-5-21-2447848828-1310731447-1641304557-13231500=u56Lnp2ejJqBz83MmsfNncnSzJnGztLLyMfP0p7Nxp3Szs/HycjPzJrIy5ybgZiQkJuXipKekYzRkJGSlpyNkIyQmYvRnJCSgcjQzsbQzc/OzN/Oz8XLzsXLyN+vsg==; expires=Fri,
19-Jul-2013 22:41:47 GMT; path=/Microsoft-Server-ActiveSync; secure; HttpOnly";
    Vary = "Accept-Encoding";
    "X-AspNet-Version" = "4.0.30319";
    "X-BEServer" = BN1PR05MB121;
    "X-CalculatedBETarget" = "bn1pr05mb121.namprd05.prod.outlook.com";
    "X-DiagInfo" = BN1PR05MB121;
    "X-FEServer" = BY2PR09CA003;
    "X-Powered-By" = "ASP.NET";
    "request-id" = "b78e1afc-74b4-4080-a8b2-c641f567d4f9";
Cookies: (
    "<NSHTTPCookie version:0 name:\"X-BackEndCookie\" value:\"S-1-5-21-2447848828-1310731447-1641304557-13231500=u56Lnp2ejJqBz83MmsfNncnSzJnGztLLyMfP0p7Nxp3Szs/HycjPzJrIy5ybgZiQkJuXipKekYzRkJGSlpyNkIyQmYvRnJCSgcjQzsbQzc/OzN/Oz8XLzsXLyN+vsg==\"
expiresDate:2013-07-19 22:41:47 +0000 created:2013-07-19 22:31:47 +0000 (3.95966e+08) sessionOnly:FALSE domain:\"outlook.office365.com\" path:\"/Microsoft-Server-ActiveSync\" isSecure:TRUE>"
Thanks!
    -Rich

Answer 1

Hi Tom,
Thanks for following up on this and providing a definitive answer. It is much appreciated.
The decision they have made to block the Drafts folder syncing is mildly disappointing.
Unfortunately, the mechanism by which they are implementing this makes it a more serious issue.
Specifically, they should not be returning a Status of 4 in response to the GetItemEstimate for the Drafts folder. That Status of 4 effectively says, "Try Again".  See section 2.2.3.162.6 of the MS-ASCMD document.
Instead, they should probably return a Status of 1 and an Estimate of 0. This would be the appropriate match with their empty collection in response to the Sync command.
Alternatively, they could return a Status of 2 indicating, "an incorrect folder was requested". 
Or they could simply omit the folder from the FolderHierarchy response.
By returning a 4 and requesting that the client try again, they can cause the client to enter a continuous (and infinite) stream of GetItemEstimate requests. By following the documentation from 2.2.3.162.6, a client would get into this loop:
1) GetItemEstimate returns 'Invalid sync key'
2) FolderSync returns status OK 
3) GetItemEstimate returns 'Invalid sync key'
4) FolderSync with syncKey 0  returns Status OK
5) goto 1
Thanks,
    -Rich