The problem is with the MS update in June. Here is an article describing what is happening:
If any filename has either 2 dots or an exclamation point and a dot will get stripped, even if it is a safe attachment (i.e. pdf or txt). So text!.txt and text..pdf will get stripped. Also note that Microsoft truncates long filenames in attachments by putting ... to indicate that it has been truncated. Them MS strips the attachments due to the double dot rule above. How very MS of them. I think the truncation limit is 71 characters but it could be shorter. I can confirm this happens to Office 2010. This update also affects calendar invites with attachments. Users with Office 2010 cannot open the attachments by double clicking them, they have to copy and paste them to their desktops and then they can open them. Does not affect Office 2016 though.
Also MS is aware of the issue and MIGHT offer a fix, but don't hold your breath. Here is the KB article describing the MS awareness and known workarounds:
Also keep in mind that one of the workarounds is to just remove the patch; however once the bad guys know that people are removing the patch they will exploit the fact that people are purposely making themselves more vulnerable and use whatever flaw was found to create the patch.
Patches are created because someone has shown the vendor there is a hole, reopening the hole exposes you to a known exploit path. Think of it this way: Road repair crews do not repair potholes they don't know about, they only fix a pothole when someone reports it to them.
Edited by computerscott2, 28 June 2017 - 07:26 AM.