Blocking specific file types as attachment in a Transport rule

Bühler Gabriel 71 Reputation points

Hello Everyone

Is there a way to create a specific Transport rule that blocks all incoming E-Mails that contain HTML-Files as attachments?

I can adjust my Malware-Policies to block these kinds of E-Mails for outgoing E-Mails, and I can block a specific set up list of file-types, but I would like to add additional file types to this transport rule.

Thank you for your Help.

Kind regards,


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Microsoft Exchange Online Management
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  1. Vasil Michev 96,916 Reputation points MVP

    Sure, you should be able to use the AttachmentExtensionMatchesWords condition, as detailed for example here:

    Though the common attachment filter under Malware policies is probably a better place to enforce this.