"Common Attachment Types Filter" and file types known by Office 365

New Contributor



I was wondering, if there is some reference or powershell cmdlet to get all the built in file types (96 are shown in the EAC) in antimalware policies:



Furthermore, I wonder which file types Exchange Online or Office 365 can recognize regardless of the file extension. I can add xlsm as a file type in an antimalware policy, and then Excel macros will also be filtered, even I give them another extension. Why are Excel macros not included in the 96 built-in lists of the antimalware policies by default?


Other palces, where file types play a role:

Transport Rules

OWA Policies

Outlook Desktop Clients


Security and Compliance



It is quite confusing that the documentation of the individual areas always describes different file types.


How do I know, which file types I can add where to get them procecced regardless of the file name extension?


Hope someone can help here.


Best regards


2 Replies
Is there no one to answer this question? Help would be really appreciated.

Best regards Andreas

Hi @AndreasMarx 

Excel Macro is still quite widespread so you can't automatically exclude it (I know sounds strange).

I think following statement clears out the situation. Inspectable file extensions are known to antimalware policies and don't really on name comparision.



Following section talks about the inspectable filetypes. Take a look if it helps you.



With those documentation I would start my scenario's.


Hope it helps.