Receiving winmail.dat files from Outlook 2013 user

You can take a look at TNEF's Enough -> http://www.joshjacob.com/mac-development/tnef.php

The WinMail.dat issue is an age old one with Outlook. Microsoft Outlook commonly formats emails using RTF, which sometimes other email clients cannot decode. Simplest solution for the other user is to send the email again in plaintext. I have fought this issue for more years than I will admit to, and it seems to hang around through many iterations of Outlook.

This is an old MS article, but still applies - https://support.microsoft.com/en-us/kb/278061 or this - http://www.pchell.com/support/winmaildat.shtml or this - If you get an email message with a winmail.dat attachment on your Mac - Apple Support

It's Microsoft's fault.

It's also their IT persons fault for being ignorant of this issue and falsely accusing you over a Microsoft issue. This issue even affected Outlook Express on Windows back when that still existed.

I personally use TNEF Enough as suggested by Duane, however here are two other options to consider.

• Kerio Connect is a commercial mail server that has built-in intelligence to detect the dreaded winmail.dat files and automatically convert them before sending the emails to users. If you don't have the option of running your own server then this will not help.
• Letter Opener Pro is a plugin for Apple Mail which will automatically detect and convert winmail.dat attachments so that you never have to see them in Apple Mail. See https://www.creativeinaustria.com/LetterOpenerPro

If you need or want a little more information, here is a good recent article about Winmail.dat - http://osxdaily.com/2016/04/19/open-winmail-dat-file-mac-os-x/

We have Multiple Macs - All are on the Latest Mac OS. People have cc'd us the same emails and some Macs see them fine others get the dreaded win mail files.

This is NOT a problem with the sender as some macs Can view them just fine.

This is considered a problem because the sender is sending a non-standard file which is highly specific to one OS.

The Macs ability to recognize the files has nothing to do with the OS version installed as you have proven. You should now determine every software, utility, and extension installed on each Mac. Determine which of those are common on the Macs without this issue. Install that software on the Macs showing this issue. OR you can heed the advice given above and save hours of work.