Mail app "no internet connection" message only with mobile data

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Hi, I'm having an odd problem. I have an Iphone 5s, IOS 9.3.3.

The mail app pops the "Can't access mail. No internet connection" message, but ONLY when I scroll down from the app and ONLY when I'm on mobile data.

At first I thought I have the mobile data off for the mail app, but I have it on. Also, if I completly close the app and re open it, it loads the mails perfectly fine (on mobile data).

To make the problem odder, when I'm on Wifi everything works fine (I can scroll down in the app and load the mails).

Any sugestions other than restoring?