Outlook 2013 Email Attachments Become Winmail.dat Files for Mac Recipients

Hi Noah-NWCLC,

Thanks for your reply.

Based on my knowledge, the issue is related to the mail app. The mail app may have some attachment issues when receiving emails from older versions of Microsoft Outlook. 

I will have to strongly disagree with that statement.

It’s a very old issue that affects a number of emails clients, not just Mail or Mac users actually. It has to do with how the email is being sent by Outlook for windows: Instead og using the regular rich text/HTML format, Outlook on your computer is likely to be configured to use a version of rich formatting that’s only supported in Outlook for Windows. Some outgoing Exchange servers also sometimes convert to that format. This has to be turned off to correct the issue for all recipients not using Outlook for Windows.

Since other clients cannot read the proprietary format, they display the plain text version of the email (that’s also embedded in the message) and the formatted version (and sometimes attachments) appears as winmail.dat

Google it up, its all over the web. Here are a few pages describing it more in details: 

https://www.lifewire.com/prevent-sending-winmail-dat-attachments-1173717

https://support.microsoft.com/en-us/help/278061/email-received-from-a-sender-using-outlook-includes-a-winmail-dat-atta

https://support.microsoft.com/en-us/help/138053/how-to-prevent-the-winmail-dat-file-from-being-sent-to-internet-users

Apple Support cannot do a thing about this issue…

Corentin

Okay, I will tell the Mac user to talk to Apple Support. Thanks again, Erick - have a good day!  ~Noah

Hi Noah-NWCLC,

Thanks for your reply.

Based on my knowledge, the issue is related to the mail app. The mail app may have some attachment issues when receiving emails from older versions of Microsoft Outlook. Given the situation, we suggest you contact Apple support for further help to check whether it can be changed. Meantime, if you need any information from us, please feel free to let us know. Your understanding is highly appreciated.

Best Regards,

Erick

Hi Noah-NWCLC,

Thanks for your reply.

Based on my knowledge, the issue is related to the mail app. The mail app may have some attachment issues when receiving emails from older versions of Microsoft Outlook. Given the situation, we suggest you contact Apple support for further help to check whether it can be changed. Meantime, if you need any information from us, please feel free to let us know. Your understanding is highly appreciated.

Best Regards,

Erick

Hi Erick, 

Thank you for that information. The Mac user is using the default mail app. If I understand that reference correctly, it says that we can solve the problem by making sure our email is sent in HTML or plain text format. However, we already had that setting in place, and the problem occurred anyway. Am I misunderstanding the reference? 

~Noah

Hi Noah-NWCLC,

May I know whether your mac users use Outlook for Mac 2016 or default mail app? If you use default mail app, based on my knowledge, there seems to be a known issue for it. Because the sender use Transport Neutral Encapsulation Format (TNEF).

Here is a reference about TNEF:

https://support.microsoft.com/en-sg/help/290809/how-e-mail-message-formats-affect-internet-e-mail-messages-in-outlook

Best Regards,

Hi Noah-NWCLC,

May I know whether your mac users use Outlook for Mac 2016 or default mail app? If you use default mail app, based on my knowledge, there seems to be a known issue for it. Because the sender use Transport Neutral Encapsulation Format (TNEF).

Here is a reference about TNEF:

https://support.microsoft.com/en-sg/help/290809/how-e-mail-message-formats-affect-internet-e-mail-messages-in-outlook

Best Regards,

Erick