Security: These file formats are regularly used to spread malware in Outlook inboxes. Among which: .js, .jar, .exe,.com,.cmd,.asp,.app,.bat,.pst,.url,.vbs .

Microsoft has decided to ban a new series of extensions to the web version of its Outlook email to enhance its security. There are a total of 38 of them, including Java, Python and PowerShell extensions, which are frequently used by hackers to spread malware via email bombs. Outlook for the Web is available with Office 365 and Exchange Online subscriptions and included in Exchange mail servers deployed on site.

These 38 extensions will join the 104 file formats already on Microsoft's blacklist. From that point on, users will no longer be able to download any attachments received using any of these extensions. Only an Outlook/Exchange, Office 365, Exchange Online or Exchange Server administrator can create exceptions by setting up a special configuration. 

The black list of the 38 extensions

 SOURCE: zdnet