Confirmed: Yahoo! email is responsible for data bug on Windows Phone

It's been whispered about and openly discussed at XDA for some time, but it has now been confirmed that Yahoo! email is the so-called "data hog" culprit on Windows Phone. To refresh, some users were reporting large amounts of data traffic being sent from their phones, resulting in some people approaching or going over their capped data limit. Yet others saw no such behavior. Microsoft finally investigated and found the source themselves but refused to name them publicly, instead they tried to address it behind doors.

Now Raphael Rivera, part of the ChevronWP7 team, has gone ahead and created some sophisticated tests to nail down the offending app.  Yahoo email has been suspected by many for some time (see here and here) but now seemingly concrete proof has been demonstrated. To sum up the technical by Rivera, Yahoo appears to be sending around 25 times the amount of data that it needs to, which is quite an increase. As a result, Rivera recommends the following for Yahoo! mail users:

To workaround this, I strongly recommend Yahoo mail users reconfigure the phone to not transmit data via a cellular connection (Settings –> Cellular –> Data roaming options). As an alternative, you can set your Yahoo account to only Download new content only on manual trigger (Yahoo Mail –> Settings –> Sync Settings).

Sounds like sage advice. Seeing as Yahoo is the culprit here, this seems to explain why some of us did not ever experience such behavior, while others did. This also means that it's not WP7's fault but rather something on Yahoo's end that needs to be addressed. Read more on the nitty-gritty on Rivera's page here.

Update: Microsoft is now officially acknowledging the issue: "Microsoft and Yahoo! have worked together to identify a fix, which will be rolled out in the coming weeks.". There also is a rare problem with Exchange Active Sync (EAS) which should be fixed in a software update.


Reader comments

Confirmed: Yahoo! email is responsible for data bug on Windows Phone


I'd really love to have been able to track my data usage, but I transferred ~10GB last billing period. Makes it a bit tough.

Changed my Yahoo sync time from every 15 minutes to every 30 minutes three days ago and my daily data usage changed from 80-110MB daily to 10-18MB. And that's with WiFi on 24/7. Thought MS had already done something, but I guess this number will drop down much more when the fix actually goes through. Have an unlimited plan so not that worried about data, but it has to be putting a hit on the battery with all that data transfer.

We hear so many issues with apps getting stuck in the approval process (GooNews), but what happened to this one? Seems like it was pushed through without proper testing.

No app. This is just setting up email on your phone. Same as Hotmail or GMail. Guess it happens when mail syncs with Yahoo servers.

I can't think of an excuse Microsoft has for not disclosing this earlier. It's possible to mitigate the damage without any OS updates so they basically left people wasting money for some reason I can't think of. Depressing...

I don't think this is all of it. My phone has the crazy data spikes yet I do not have my Yahoo mail set up on my phone.And it always happens at night, around 11pm. The mail updates happen at intervals throughout the day.

Why is this Yahoo's fault? IMAP is a protocol where the server (yahoo) will hand you whatever new emails you have when the client (phone) asks for them. IMAP is not *push* email, the IMAP server has no ability to reach out to the phone to either push or retrieve anything. The only communications are when the client device asks the IMAP server for something.. This is an MS problem stemming from their (as usual) non-standard implementation of a standard protocol...