So the android mail app just ate my data plan over night?!

Screenshot_2013-04-05-14-55-31_medium

via www.dropbox.com


Screenshot_2013-04-05-14-54-57_medium

via www.dropbox.com


This morning something strange happened. I picked up my Nexus 4 and it showed me that the data usage warning of 160 MB I had set had been reached. I couldn't believe it because the evening before I had checked I had used 80 MB, so I clicked on Data usage and was shocked: the native mail app had used 80 MB over night! Although the phone was on wifi! Even funnier if I search for the mail app in the settings and look at its saved data I can see that it has onl 20 MBs saved locally, so what happend?

Is this a bug or a late 1st April joke? By the way I use 3 imap mail accounts with it. One iCloude and two t-online.de.

They are set to get their data every hour