If you are getting mail bounced back to you with the following error:
550 This message contains malware (Win.Exploit.CVE_2016_3316-1)
then the chances are good that you need to do the latest Windows update.
Please see the following links for info. Short story – Office has a critical update and you are required to install that update in order for your attachments (word and excel) to be passed through most mail servers.