Why was my account banned?

I received an email this morning. It said my account participated in "MMRBoosting". And it was banned till Nov 10th. But I did not do anything about "MMRBoosting"!!! Can you give me some evidence and explanations? I am quite angry about that. I am diamond 5 last season and now diamond 5 81 LP. My border has been removed yet. I am so sad.
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