High mobile data usage / email app

I am facing a high usage of mobile data with my mail app since yesterday.
In two days I was on mobile data for 4h each day. The result was a usage of 300MB of mobile data. I did not send/receive more than 20 emails. No major attachments.

Right now, I have no guess where this could come from. Anybody who could help?

I do have 6 rmail accounts but my usage is not such high

in a months time you mean…
(and mine is not the apps total consumption, but only mobile data)

That.s also only mobile data