Use the combination of block sender/sender domain (more at http://support.microsoft.com/en-us/office/block-or-unblock-senders-in-outlook-9bf812d4-6995-4d19-901a-76d6e26939b0 ) and email rules (more at https://support.microsoft.com/en-us/office/manage-email-messages-by-using-rules-in-outlook-c24f5dea-9465-4df4-ad17-a50704d66c59 )
They are quite effective
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hth
Marcin