I recently had to block password protected office and zipfiles on Exchange servers. The process is below:
Exchange administrators can create transport rules by going to Exchange Admin Center > Mail flow > Rules. You need to be assigned permissions before you can perform this procedure. After you start to create a new rule, you can see the full list of attachment-related conditions by clicking More options > Any attachment under Apply this rule if. The attachment-related options are shown in the following diagram.
Choose is password protected and you’re protected.
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