On 13 June 2017 an update for Outlook 2007, 2010, 2013 and 2016, was installed. You may now find some attachments are blocked.

This security update resolves vulnerabilities in Microsoft Office that could allow remote code execution if a user opens a specially crafted Office file.

This issue applies to files that have two dots or an exclamation mark in front of their file extension. The sender of the message has used two dots in the file name which is suspect behaviour and Microsoft is now blocking such named attachments.

You have to ask the sender to rename their attachment correctly and resend it.