If you have a website(which you do) and you have a contact form (which you do) then you will undoubtedly have a mailbox that received the message from your contact form. Now no matter what precautions you take, you are still seeing a lot of spam. If you need to report mail on that mailbox you may see the following message:
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You have insufficient rights to see the content.You do not have permission to report for this mailbox
So what needs to change?
Well it just means that you need to be given 'send as' permissions as reporting junk entails sending a message from that mailbox (the shared one you are accessing) and so you need to get the Office 365 administrator to give your mailbox send as permissions in the exchange admin page here: