We have Exchange 2013 in our domain, and one user cannot see .doc attached files from another specific user. If I send him .doc attached files, he sees it just fine. In the sender's outlook, the mail displayed with attachments. I've tried to search through google but there is an only similar problem related to executable extensions such as .exe, .vbs, and etc, but .doc is not executable and in the past, this user didn't have such problem. And by saying "he can't see attachments" I mean he really can't, there is just a usual mail without any attachment icons.
I've also checked that sender sends the mail in HTML format.
Have someone encountered such a problem?
P.S Sorry if I made some mistakes, English isn't my native language.